To me Fallout is the anti Elder Scrolls Scifi game that tries to be the opposite to everything Bethesda does with their flag ship game.
When I played far harbor I noticed a possible change in course that I hope they can continue. It would be very important for the world to evolve, because I don't see how or why the apocalyptic world would stay that way for long after Fallout 4 with the PC creating all of those settlements possibly even being director of the institute, that changes the course of the entire game.
I fear to some degree that they may try to hard in making it doom and gloom, there is no reason to think society couldn't be rebuilt after fallout 4. If they keep going the path they took with that game with Fallout 5, I think the whole concept of this game will change.
For the next game to be anything like New Vegas or Fallout 3 and the past games, they would have to either go back in time or ignore the progress that was made in fallout 4. That's not to say that the future of Fallout will be what I am thinking as delving further into a Scifi lore which I hope they do, as it more than likely will continue as a post apocalyptic universe and leave more to be desired.