I think the biggest change that has occurred in the last 6-8 years is
DVC being exposed to the Internet age. Whenever we message board denizens offer advice to current or prospective members, the message is always are always the same:
* Buy where you want to stay
* Book right at 11 months
* If you want to book a non-Home resort, call right at 7 months
Years of offering that sort of advice have changed the entire landscape of how members book their trips. The days when members can call on just a month or two's notice and have multiple resort choices are gone. You can point to SSR as a catalyst if you wish, but IMO the change was inevitable. Other timeshare systems face the same issues. You're never going to have an environment where supply and demand are even across the entire system.
I'll also point out that given the varying sizes of the resorts, it's really hard to make even educated guesses about member trends. Rarely are resorts booked to 100% occupancy by their owners at 11 months. Let's say that resorts average 50% occupancy before the 7 month window arrives. If so, the approximate number of rooms available at each resort goes something like this:
VWL: 68 vacancies
BCV: 104 vacancies
BWV: 200 vacancies
OKW: 270 vacancies
SSR: 440 vacancies
Now let's assume that demand for each of those resorts by non-owners is EQUAL. If 200 members want to book each of VWL, BCV and BWV at 7 months, those resorts will reach max occupancy and most will have to turn people away. OKW and SSR can both absorb 200 more reservations and will still have room for more.
With the growth DVC has experienced, building large resorts like SSR, AKV and BLT (which, IMO, will double in size when that second tower is eventually built) are necessary. The biggest mistake DVC made was building the tiny add-ons at VWL and BCV in the first place.
I doubt there is anything Disney could do to return us to the days of VWL and BCV bookings just 1-2 months out. Even if SSR were half its size you would still be losing out to owners of every other DVC resort who occasionally want to try those smallish properties when their 7 month window arrives.