Disney can't afford to let the bottom fall out of the resale market. It's one of the major ways in which
DVC distinguishes itself from other timeshares: it holds value. Besides, there is a relationship between resale and retail prices. Yes, other timeshares sale 20k plus contracts that can be bought on Ebay resale for a few bucks, but they must use high pressure sales to do so.
Disney will use ROFR to keep prices up, and they will eventually make extensions available.
Look at the proposed expansions of VWL and BCV. They will have to sell new with 50 year contracts. Disney can't lose half of its MF payers halfway through those new contracts. They'll have to bring those other points along. Keeping the current owners will be easier then trying to resell a 40 yr old resort as new in 2042.
When I bought BCV, I made the calculation that extensions would be offered down the road (either with the rollout of new points with expansion or around the 15 year mark (2027) where resale prices will start to really get squeezed). If I'm wrong, 27 years at BCV for $84/point was still a bargain.
I don't think I'm wrong.
Even if DVD decides to tier off expansion into a technically different home resort, the option will still exist to sell 2042 points and then buy 2069 points and be at Beach Club for cheaper than whatever the direct price will be (and until I'm older than 100). No matter how I looked at it, the downsides to buying a 2042 resort wasn't a serious factor in my purchase. This is a problem that will have a solution when the right time comes.