Half Life 3

Valve doesn't need to make games anymore. Their corporate structure allows for it, but relies on people at the company wanting to work on it.
But if they don't, it's not really a problem. The company is doing fine.
I think they just lost interest. They got back to it with Alyx because VR was exciting and new territory to explore.
- This is the correct answer I think. They're also not interested in releasing sub-par games, and again like you say they don't need to release games at all to make money anymore. So if they're not that interested and haven't come up with anything conceptually/mechanically that reaches the high bar they've set for themselves, it makes more sense to scrap/postpone.
  Their reputation is much more important, and they're just not going to half-ass Half Life 3. It will come out when they feel they have something truly extraordinary, or it won't come out at all.
- Pretty much this. I'm fairly certain that I read years ago that Gabe just wasn't interested as well. Which fair enough valve don't need to develop games now because they have to but because they want to.
- They seem to release these games as some sort of tech demo show showcasing what they see is the future of games. One has the set peice structure of game design, two was the physics engine, and Alex was VR. So other then the continuation of the time line, half life Alex pretty much was half life three. Also they know the hype/meme train has been building for so long that nothing will be good enough. Like Duke nukem.
- Don't worry we have Alyx 2 to look forward to

We know the answers to this. First, we got Half-Life: Alyx, which is a phenomenal Half-Life game that happens to be a VR game. Slight spoilers, but to say that Half-Life 3 is promised at the end of that game is an understatement.
Second, if you've already played Alyx, Keighley put out The Final Hours of Half-Life: Alyx, which has a full timeline of everything they worked on since Portal 2, including cancelled games. One of those games was Half-Life 3. It would have been a game with procedurally generated levels interspersed with static set pieces, which sounds similar to a single player version of that game The Crossing they were working on. If you ask me, that design makes plenty of sense for putting a bow on a series with a time- and space-hopping protagonist in a series that always ends with cliffhangers. It didn't come together though, so it got cancelled.
Alyx was put together in part because letting all of their employees dictate their own projects was not getting the same results that it used to, so there was a bit more direction with the project than Valve had had in the years prior.

The reason no one is making HL3 is because no one wants to, at least not long term.
Idk if you know much about how Valve is structured as a game studio, but it's a bit atypical. It's not like Gabe Newell comes in and says "today everybody starts working on HL3", projects get greenlit and then whichever employees want to work on them are free to do so, and if they decide they're uninterested, for whatever reason, they can leave the project.
What this means, is that if a project starts to pick up steam (no pun intended) within the company, more and more people join in, and this creates a passionate team. Various Half-Life projects since Ep2 have been started, none were finished (until Alyx), not because they were decisively axed for more corporate reasons like many other games, but because for one reason or another, the devs became uninterested or burned out, and went to work on other things they actually wanted to work on.
I think at this point, the only way we'll ever see HL3 is if a team comes up with something completely groundbreaking and is absolutely dedicated to getting it done. Apparently, there just hasn't been that winning combo yet. I can't blame them, because if they half assed any aspect of it, they'd never hear the end of it.
- That description of how the teams are structured sounds completely made up. They'd never get a game finished if the company was actually structured that way. I've personally never worked for a company that would just let me project hop when I felt like it.
  You'd be starting over constantly.
  
  And yet that's exactly how they operate!
  Valve: How going boss-free empowered the games-maker
  ... But you're right that it is often considered the cause of many of their problems: Valve's unusual corporate structure causes its problems, report suggests

The hype train is absolutely dangerous.
The anticipation for HL3 would be terribly high, and so would be the expectations of millions of lovers of the franchise, making sure anything other than a perfect game would be met with lots of negative reactions.
And it's not just about a single game either. A bad HL3 could end up tarnishing the legacy of the other titles, forever ruining what is now a beloved franchise. Remember what happened to Game of Thrones? Who would ever risk something like that happening? Or, speaking of games, look at how much goodwill Bethesda burned with the release of Starfield.
- Duke Nukem Forever was the victim of this (among other issues). Expectations were so high, by the time it finally released it couldn't do anything but be an absolute failure. It still sold well, because of the hype, but the game was total trash and ruined any chances of a new Duke Nukem for a long time. Part of it is also internal, the game gets delayed, people get hyped up and voice their expectations. The devs hear those expectations and see their game doesn't live up to it and delay the game to make it better. It's an endless race you can't ever win.
  
  Duke nukem forever didn't tarnish the older games IMO. Because the games barely have any story to begin with, they are mostly ranked for their gameplay, which is still awesome to this day. At least for 2 and 3d.
  Duke1 is nothing too special. But Duke1 wasn't even too special at time of release.

I can’t think of a game that Valve has released just to make money except for Artifact which totally flopped.
From what I understand, Valve has a non-hierarchical internal personnel structure and projects are started because someone has an idea that other people at the company like and want to work on.
Half-Life 3 won’t get traction inside Valve unless it has something to push the envelope like the other main-line games had. Half-Life had unrivaled first person storytelling. Half-Life 2 has unrivaled physics to play with. Half-Life Alyx had an interactive environment unlike anything else that exists even still. My money says if Valve can’t think of something gameplay-wise that’s as enticing right now as any of the previous games had when they were released, they don’t care that the story is still on a cliffhanger.
- Like Gaben has also said, if they did release it it probably wouldn't live up to all the impossible expectations.

Half Life was always about pushing the boundaries of gaming. The first Half Life with their combination of story telling in a 3D shooter environment was absolutely at the sharp end of the field at that time. If you've seen the Black Mesa documentary you'll know why HL2 was such a hit and how it was revolutionary at that time. After that they did some DLC, but Valve wasn't happy with what they were doing. It wasn't groundbreaking, it was just creating content for the sake of content. As they didn't need any more money from creating games, they opted to not create HL3. It wasn't till VR became more mainstream they again tried to do something at the sharp end of the field, by creating HL Alyx.
I don't know what would prompt them to ever make a HL3 if such a thing even exists.
- Episodic gaming as a format was the groundbreaking feature. It was supposed to be the future of gaming.
  
  It was, devs just realized they don't have to break the content up into episodes or actually complete the first part they release, and can call it early access instead.

I think at this point, no one can ever live up to the expectations for the game and Valve is too afraid to fuck it up.
- I believe Gaben said this specifically at some point

I think HL3 will only happen to push some frontier in gaming, like they did with Alyx and VR. It's the only safe move with that franchise and all the hype
- Gabe has always said he'll make HL3, "when the technology is there".
  No idea what it means, but it seems he at least has a vision for what the game should be.
  
  Alyx used PBR a technology already dated compared to Raytracing and it looks better than most games with Raytracing. We're there, man.
- This is exactly it. Most of their major titles utilize some new tech or groundbreaking feature and whatever they have planned for HL3 is just not ready yet.

Valve isn‘t publicly traded (AFAIK) so they don‘t have to squeeze every last penny if they don‘t want to. And Steam revenue alone can fund anything gabeN wants to do. They don‘t have any ideas for HL3 they‘re satisfied with so they don‘t make it. And I respect that a lot TBH.

Valve used to make games, now they make money
- And that's why they can afford investing in VR and in games like HL: Alyx. I enjoyed it very, very much.

It's a tough one as it's on such a pedestal now

What you are asking for is for Valve to start behaving like developers like EA and Activision, who keep milking the crap out of their franchises with one bland generic release after the other for a quick cash grab.
The fact that Gaben doesn't force his employees to work on the game just to make money is the reason why Half-Life games are of such good quality. The employees at Valve work on what they are motivated to work on at the moment. They aren't being given arbitrary deadlines from overhead either. This is how we got amazing games like Team Fortress 2 and the Portal games too. Both Half-Life games were major milestones in video game history by pushing the envelope. And currently, no Valve employees believe that the conditions are currently set for this to happen with a new Half-Life 3. It would never meet the hype if they tried right now and it would be a huge disappointment.
Half-Life 3 isn't vaporware either as Valve openly admits that they are not working on it at the moment.
Just accept that great things can't happen as often as we wished they did.
Speaking of Team Fortress 2 and Portal, I have been around to witness other attempted iterations of what TF2 could have been been, only to be abandoned by Valve because it wasn't good enough. Then Valve finally got their vision for what the game ultimately ended up being and then suddenly everyone was motivated to work on the game. The first Portal game was also an experiment that motivated Valve employees to work on the sequel. Hopefully one day there will be a lightbulb moment in Valve and everyone will be motivated on working on Half-Life 3 and the resulting product will surely be worthy of the name. But you can't force it to happen.
Hopefully it will happen while Gaben is still in control of Valve though because there is no telling what will happen to the company's unique culture and philosophy after that.

Valve these days don't make things just to make money. They only make things that interest and excite them. HL3 would most likely just end up being more of the same, which isn't exciting from a designer or developer point of view. They need a hook to get excited about it, and until that happens it's just not worth the time or effort to do. In the meantime, they're making plenty of money from Steam sales.

I think it’s 100% that steam makes so much money on its own. Valve stopped being a game developer once steam really took off and became the behemoth it is. Valve is in the e-commerce business, period.
I loved Alyx too for what it’s worth but my expectations for the future are dim.

If Valve can't do something that will push their business and the whole industry forward, they'll just do some other thing that will.
Doing sequels after sequels will only stagnate the franchise, making Valve lose time. For that, they rely on publishers like Activision, EA, and Ubisoft among others.
- You mean sequel? Valve doesn't do "sequels"

My theory is that it already has been released on Steam years ago, but not as a Valve title. It has sold millions of copies in a Humble Bundle, but nobody has ever played it.

HL3 is cool but it will never be better than Polybius, IMO.

Valve can't count to 3

I have a theory, they are gonna do an orange box kinda thing with it.
All the threes of every game in one. Plus a much newer engine with minimal restrictions.

If Valve does ever make HL3, it's going to have to be ground breaking. Every Half Life game redefines what gaming is capable of. Eg HL: Alyx was an insane demonstration of what VR can do. I do think it'll happen eventually, and may even partially be in development right now. But I don't think we'll hear anything about it for a very long time.