Well, I guess we can wait to see (and get our hands on) the game, but I don't think basing Fallout on Oblivion (and by much the same devs, to boot) is a spectacularly good idea. What I have seen of the game literally looks like STALKER on Oblivion's engine, plus the "bullettime replacement" aiming. I think Hellgate London proved that mixing RPG with FPS is hardly a viable mechanic. You either get a ridiculous FPS where your hit/miss and damage are determined by your stats, or a lousy RPG that's more of a FPS "with elements".
Really, it's not that I don't like people trying to mix genres, but these people are trying to mask a possible game design failure ("possible" as in they are not sure whether it's a failure or not) with a well-known name and setting. They could make a new name and make their game all they like, but "Fallout" is a classic, and especially "Fallout 3", with nothing else, would indicate it's a continuation of the genre. There were examples of games switching genres, but then they had sub-names to indicate that. CnC:Renegade wasn't called "CnC 3" because it was not continuing the original game. Were Bethesda at least to name the game "Fallout:Decontamination" or something, I think people would take it better. I mean, really, what if Blizzard were to announce that Diablo 3 would be played from 3rd person, or StarCraft 2 will become turn-based?