Actually, once you open that "space-time tear" can of worms, the what-if factor tends to increase by ridiculous orders of magnitude. I'm inclined to speculate you don't have much experience in the nerd-wrangling arena, sir. This is the stuff truly horrible fanfiction is made of.
::pushes glasses up authoritatively on nose::
There's no reason NV shouldn't be official, as it ties in nearly seamlessly with pre-existing canon. As to which parts, well, we'll just have to wait and see. The safe assumption is usually that the goody two-shoes player character is the one that went gallivanting through the wastes, so it's most likely going to be NCR or an independent Vegas. I don't see them wanting to keep House around as one of the series' brass tacks, but I could've missed my guess.