I don't pretend to be privy to the issues to building new resorts (soil, space for runoff etc), but looking at aerials the eye test says that Bay Lake is underdeveloped. Disney long ago envisioned more rooms closer to MK, so while Wilderness Lodge certainly helped closed the gap left by the never-developed resorts, there likely still isnt the room capacity near MK that Disney would want. If they can't do more around Seven Seas Lagoon like originally planned, maybe they'll do more around Bay Lake. Again, I have no idea if it's even possible (still doing soil studies!), but it's at least plausible.