Off the top of my head, there are several ways in which a "sale" could go down:
1. Sell the DVC resort ground leases. DVD doesn't actually own the land on which resorts site. It's leased from another Disney entity. Disney could sell that land and the new owner would have to honor the lease at its stated terms.
This is extremely unlikely to happen. Although Disney has sold some land on the fringes of WDW, I cannot see any value in selling large plots in the middle of the resort complex.
2. Sell Disney Vacation Development. This is the business unit which builds and markets the resorts. The buyer would receive any unsold inventory and the rights to the buildings after our current deeds expire. They would probably also get the right to build and sell other resorts on Disney property and perhaps to use the "Disney" name in some form.
Existing timeshare resorts owned by members couldn't be "sold" to another entity because...we own them. At least for the next few decades. In other words, there's not really anything DVD could "sell" of BCV, BWV, Vero, etc. because we owners (members) have deeded rights to the property.
Again this one seems remote due to the expiring leases. Come 2042 / 2054 / 2057 / 2060, DVD will recoup millions of points to sell all over again. Unless the price is extremely high, why give those rights to another entity? And if you're that other entity, there's little reason to pay a high price for a revenue stream you cannot fully realize for 30-50 years.
3. Sell Disney Vacation Club...the management company. IMHO, this is the move that would be most likely to happen, if any. To a timeshare manager, like Marriott there would certainly be value in adding the Disney resorts to their program. Member ownership would continue. We would still have priority booking at our Home resorts as guaranteed by the POS. But most other aspects of the system would be subject to whatever changes the new manager may implement.
Disney Vacation Development would still own unsold points, recapture ownership of existing resorts as contracts expire and build/market new destinations. The new manager of "DVC" would get the 15% annual management fee and be able to market Disney-based resorts as part of their program. As one poster mentioned, integration of cash/points reservations between Disney and an outside manager would be a challenge...but probably not an insurmountable one. (Although it often seems that way with Disney IT.)
4. Farm-out management of the Disney resorts. In this case there probably wouldn't be any ownership changes but Disney would contract with another company to operate the resorts. Instead of our dues paying the salaries of Disney CMs they would pay the salaries of employees of another company. This is basically outsourcing to the max.
This last option is probably within the realm of possibility, but Disney hasn't really given any signs that it is interested in getting out of the business. A few years ago Disney actually signed an agreement to manage hotels in Anahiem's Garden Walk which were to be owned by other entities. That project is stillborn at the moment, but the existence of the agreement suggests that Disney was more interested in expanding its hotel management rather than getting out of the business.
This would likely impact all resorts, DVC and non-DVC alike. Changes to members would be minimal (or nonexistent)...just like when valet parking was outsourced. In fact, conditions could actually improve at resorts if the new company proved to be a more effective hotel manager than Disney.
I'll add that any agreement could include components from multiple options above (i.e. sell both DVD and DVC.)