I do understand
naossano's thinking, that eventually we should see the world being rebuild again.
Against that I have no problem, I don't want the Fallout world to forever remain a crapsack world, that is boring.
But I think the period after the war, the emergence of new civilizations, to the point that nations start to expand into the wastelands of the world, re uniting settlements again, and eventually become somewhat like the nations of old is where the 'Fallout' period would be officially over.
Sure, outside the walls there could (and would) still be anarchy and lawlessness but it is not as if our society today is completely governed by law worldwide.
And there are still plenty of mutant critters and other after effects of the war that will probably linger on for a long time.
But there would not be such a focus on basic survival and rebuilding as there is now in the setting.
Though we class the Fallout games now as sequels I think that eventually should also expand out into 'sidequels', stories that happen roughly at the same time of another game's story, but in a different place, far removed from the other game.
This way developers would have more room to create games and expansions without having to keep the world 'in ruins' and having to explain why it is like that still decades later.
And prequels honestly don't have to be bad but they should not interfere with the other games, so again in a complete different place.
For example; I had planned the Fallout Texas setting to take place after Fallout New Vegas and the second Battle of Hoover Dam, but it could take place during the same time. If the Legion appeared in the Texas Wasteland it would be because while the Caesar is busy with the campaign against the NCR he has send some of his other Legates to expand Eastwards.
He probably runs multiple campaigns at the same time.
Large factions like the BOS and the NCR have multiple bases, forts and bunkers out in the Core Region, so while the Courier has dealings with the NCR army and BOS Mojave chapter, the Ranger (made up player character) could be doing quests for or against the NCR and the BOS in the Los Angeles Wasteland in some sort of sidequel to Fallout New Vegas.