If Lemmy and Mastodon continues to get popular, we will eventually get Instance wars.
If the descentralization of social networks continue, we will have to prepare for the eventual rise of the instances wars, where people will start to fight about which instance is better and which one is weird to be in and so on, but that's for the future of us all.
My personal hope is that the ActivityPub standard prevents this from happening. After all, I've seen decent federation between Lemmy and KBin and they're entirely different platforms, nevermind a fork of the same software.