The Boneyard would be cool, but its basically a normal city by FO2, and by NV its pretty populated. So they would have to set it before FO1 or something.
Personally I'd love them to do Denver a few years after New Vegas. We could learn more on Caesars Legion maybe travel to Fort Abandon and build it up. Or maybe do one in Seattle.
Miroku_of_Nite1's comments