Conferences that big don't care about one wing of Yacht Club, just like they don't care about one building of Grand Floridian or the lousy views at Jambo. If Disney needs to flip some aging hotel stock, Yacht Club is on the chopping block.
Coronado has space. If Skyliner goes to Coronado, they have tons of space to the north between Coronado and TTC.
They absolutely do - convention attendees want to be near the convention - they don't want those DTD rooms - frankly they'd rather not be over at the GF because you need to take transportation to get to the session. At the point at which you outgrow the room availability close by you start to look at places where you don't need to bus your attendees around - the convention center area in Orlando, Vegas, Indianapolis.
I've run conventions and I've been involved in moving them due to lack of hotel rooms nearby. There are two big reasons you pick a location - will the convention space be sufficient for your sessions and activities and are there enough nearby hotel rooms. Then you get to "do our attendees want to go to Boston/Vegas/Indianapolis? and what's the cost." Big conventions don't get away from using buses to ferry attendees around - but they do want to minimize that, both because its expensive to provide buses and because the rooms near the sessions have the most demand.