Jim Cojones
It Wandered In From the Wastes
Fallout 1: South California.
Fallout 2: North California, south Oregon and west Nevada.
Van Buren: East Nevada, Colorado, Utah, New Mexico and Arizona.
Fallout 3 = Downtown Washington DC and the surrounding desert. WTF?
It will be horribly boring to go from Boneyard to the Glow by foot. Bethesda isn't interested in making any other RPG than open-world FPP sandbox game so relatively small and crowded world is the only thing which we can expect from their game.
It should be obvious that developer's preferences are much more important than some bullshit like postapocalyptic feeling of desolated world.