Land is an issue for YC.
Also, while cannibalizing rooms seems to go along with additional units, on it's own it does not do much for increasing room capacity/attendance. (Then again, Poly DVC only added up to 8*20 = 160 people on property any given week). But DVC occupancy rates will probably always be higher than that of regular hotel rooms.
However, Disney has long been rumored to looking out ways to outsource the hotel portion of its business, and, to some degree, conversion of hotel rooms to DVC rooms is a form of middle ground on that front.
My guess is you would see something at Fort Wilderness First, or even the rumored one in the Caribbean Beach Area.