...a REALLY good question...and an interesting thought, Woody. I've always viewed milestones such as this as "stop" signs rather than "do not enter" signs. In other words, at a stop sign, you just have to bring your vehicle to a halt, evaluate the situation and then decide how to proceed. At a do not enter, you just grind to a halt and tghen go away. Who knows what will happen when the date arrives. We will all come to a stop signs and review what options are there....but as Woody rightly says, Disney controls all of the options.
My vote is that they get torn down.....and I've always thought that it is a positive that there's an ending date....most timeshares go on forever and I've always thought having unknown costs looming to try to fix up a 60 year old building would not be fun!!