Well...
0. If Troika had still been around and had been more successful with Vampire: Bloodlines they would have owned Fallout.. Lots of 'IF's and purely hypothetical, but I am not really sure that Fallout would have gone 3D the way Bethesda did it - it would probably have happened eventually along the lines of Bloodlines. It makes me cringe to think that Bethesda actually did some good for Fallout, but I think they deserve a bit of recognition for it. It's just really too bad that they own it.
1. If InXile wanted to, they could do it. Even though the constant name-dropping of Fallout in the Kickstarter context of Wasteland 2, and the incessant boasting about the Godfather of CRPG being back, made the end result look much worse to me, it was pretty good and entertaining game.
They would need some help with party dialogue and content and an all-powerful executive critical eye to avoid mixing crap-design with huge walls of text.
2. If BioWare did it, I think it would only be great if it was something like "Fallout: The Old Republic" divided into at least two opposing sides, Humans vs. Mutants, each with four separate classes, with two branches each.. and regular updates and new content.. Lots of replay value.
But that bloody dialogue wheel, that I just never can get used to, would have to go in favor of fully fleshed out dialogue lines.
3. If Obsidian did it, erm.. After what a colossal disappointment PoE was to me I don't think they have the nerve, passion and skill to produce anything I'd like. It would just be some boring, bland and balanced bullshit. They would have to go back in time and pick up the old crew, including the guys that went to form Troika to produce anything worthwhile.. Most unlikely.
Well, I really enjoyed Old World Blues, which was the only real Fallout to me, but it was like the last 'gasp', a blast of the past of that special Fallout spirit that seduced and turned me in the first place back in the nineties.
Also, I always wanted to be able to play as a Mutant in the Masters Army. It was a huge disappointment to me that being dipped in the Vats went straight to Game Over.. But that was in context with Fallout 2.