I'd go with London/ that sort of area. Would be nice to see what happened elsewhere in the world.
Also, England would probably get dragged into that war anyway.

I doubt they will do any overseas Fallout; the very essence of the game is retrofuture Americana. The next game being set in Nevada confirms that..

Didn't know it was based in Nevada.
Well at least I know something about the next.

Would like to point out though, that with a new company they could do different things.
I'd like the essence to stay there, but have a new background.
There's so much you could change. New everything.
Vault tec would probably stay, but new opponents, a weaker government presence,
A main group like the BoS only with different intentions, protection of the people over Technology.
I donno... I guess I'd like to see it as a more modern post-apocalyptic ground.
The tec we'd have expected to see from decades from now, unlike tec from the 50's.
Fallout was good, but there's other things you can do.
It would probably have to be a different named game, separate universe from fallout it's self.
Possibility's are huge though.

There already is a thread on this subject http://www.gamesas.com/bgsforums/index.php?showtopic=979897, I suggest you use it, no point in having two threads.

There is also an http://www.gamesas.com/bgsforums/index.php?showtopic=982132, or "Fallout 4" if you will.

I'd like to see a Fallout 4 installed to my PC with a crapload of mods.

Use one of the linked topics please.