So Overture seems to have time travel involved?

Seems interesting and also kind of makes sense given that the story of the game seems, more or less, rather closed and finished. There is a character shown in a post-credit scene that will likely play a larger role in the DLC but still makes sense to use time travel in some way or shape.

You could argue that they should have written the ending differently for it not to require time travel shenanigans in the first place, but we'll have to see more to judge, I guess