I say it will resemble New Reno no matter how you twist it, and that again New Fans will be hard pressed to find the originals, as a majority of stores don't carry it in the US, and to make matters worse most used game stores don't buy PC games anymore(Most have stopped buying Xbox games) where I am, unless locally owned, and you'd have more luck finding a Pirate Cart for the NES there(See Multicarts, Wisdom Tree/Color Dreams, and Tengen). I'm not saying that Vegas Should have next to no backstory, but you'll probably have to live with another New Reno-esque scenario with the Mobster-Esque characters, the drugs, the gambling, etc. I'm certain it will be more than a power struggle, to say the least, since the game is definately going to be centered around Vegas and will be forced to contain a longer story.
Worst Case Scenario for Fallout would be BoS(the console one) all over again.