They can't do that. It's in the declaration of condominium for all the resorts that every member participates in the
DVC system, and every owner of a portion of the condominium is a member of the DVC system. Moreover if they did do that, it would just make life worse for the other DVC members who bought direct, because they'd have a harder time staying in other resorts.
The things they can remove, either for everyone or just some people, include:
- Shopping & dining discounts.
- Annual pass discounts.
- Tables in Wonderland discount.
- RCI exchanges
And I'm not actually sure they'd want to restrict RCI exchanges; I think they make money on them.
Basically they can't take away your ability to book DVC resorts. That's what you're paying for, that's where the value is. The other stuff is miscellaneous conveniences and minor discounts. The exchanges for cruises and so forth are actually financially a loss over just paying cash.
Also, keep in mind that any time DVC reduces the benefits for resale customers, they reduce the resale value of everyone's memberships. If you ever think you might want to sell your membership, you should be upset that Disney has this two-tier thing going on. It could cost you money down the road. If they add more restrictions, that's dollars Disney is taking out of your pocket if you ever need or want to sell.