True NCR can take Vault City without Redding but the Chosen One does help out. If Vault City had no intrest in expanding why would they want Redding. They may be xenephobic but this does not mean they don't want more power.
Vault City isn't interested in expanding. They wanted Redding only for the resources, Vegas has nothing to offer them. In fact considering their stance on New Reno they would go out of their way to avoid contact with Vegas. Vault City has no tolerance for vice.
Still it's pointless to go on about it we know what happened. Chosen One helped out NCR and they grew to the power they are now.
Okay I'm only going to say this one more time, we don't
know anything yet. Have you extensively played New Vegas before everyone else here and know something that we don't? The NCR could have expanded to Vegas within 40 years regardless of the ending they got in Fallout 2.
I just hate ambiguous endings. I like having clear endings. To me FO2's good ending is the canon ending and I hope the Devs make it so. If not it will take some of the joy out of New Vegas. I am looking forward to stories from Marcus about the hero in the West (Chosen One) and even the Vault Dweller. I want to hear about the good things done in FO2. I don't want to findout the Chosen One was a scourge of the wasteland or has become forgotten by the NCR or anyone else from the west.
And other people would prefer the Chosen One to be evil, or even neutral. I'd rather the Chosen One's path be kept ambiguous so that it doesn't trample over how people played Fallout 2, and so I don't feel obligated to play Fallout 2
like so when I replay it. What's the point of offering all of that freedom if you're just going to canonize certain epilogues in the sequel? It's best to either keep the player character's choices ambiguous, or use a save game importing feature like in Mass Effect 2 and Dragon Age 2.