The answer is maybe. The POS documents for the pre-Riviera resorts, including the Declarations and applicable DVC Resort Agreements, and also the Purchase Agreements, all have terms which declare that any owner and any Club Member, including resale purchasers, have a right to use the DVC Reservation Component to reserve DVC Resorts other than their own. Thus, if Disney obeys all those prior representations and rights contained in those documents, it will not prohibit a resale purchaser of the pre-Riviera resorts from reserving non-owned DVC Resorts.
Nevertheless, the answer is maybe, because in the last three months, Disney has decided that the official documents, and its representations that were previously made, do not control. In fact, it has even told members in the last couple of months that it is not bound by prior written representations. Moreover, if it had followed the actual representations and rights set out in the official documents, it would not have added Riviera as a DVC Resort via a DVC Resort Agreement that contains any restrictions on resale owners ability to reserve Riviera.
Some may feel safe because Disney has typically grandfathered existing owners, and thus, whenever it creates new restrictions for resale owners, it only applies them to those who purchase after the new restrictions have been created. But based on what we have seen lately, no one should feel safe with this new Disney timeshare company that has replaced the one that at one time was considered the model timeshare company.