Well, NCR is probably well on their way to work something out about good transportation. First of all, we already know they got alot of vehicles (they got functionable trucks, and studieng the Wiki they seem to work. Along with trains, as they are building train roads to Vegas using the convicts, plus the captured vertibirds they got from the Enclave, and looking at the one Kimball uses, they seem to work fine with no fuel problems whatsoever).
Also, in tactics vehicles are plenty, and even though the midwest brotherhood was more awesome then others, someone else should be able to develop or scavenge working vehicles, so vehicles in the next game is not unrealistic against the fallout lore, so people stop saying that.