Thus pissing off three quarters of those who played New Vegas? Actually scratch that, a half, as if they do decide to canonize the ending of New Vegas the NCR will win.
Why would they be pissed off though?
There needs to be an official storyline in Fallout, canon.
If some people get pissed off then so be it, but if they decide that they wanted an event canonized for future purposes then so be it.
No reason to be mad about it.
I just think a lot of people are spoiled by Mass Effects continuation and expects that "their" choices matter.
But in the official story, in the official fictional universe, there can't be a bunch of "what if's", if there are then it's just going to be harder and harder to make each game in order to not contradict what a player "might have done" in a previous game.
So when we play the game we get to see the what if scenarios in the ending sliders, but that's it.
We get to see that "Well, if the Courier/VDweller/Chosen would've done this then "this" would've happened".
Anyway, shortened version: When it comes to the official story and it's universe then our choices we made doesn't mean crap. It's all about how the developers want to proceed with it, what they wanted to happen in order for their next game to make sense.