I have no doubt that there are quite a few DVC members who would do a resort-only stay, but I think the problem for Disney is that they don’t get much revenue from DVC members staying on property and not going into the parks. The only incentive to reopen for DVC members is to start getting themselves out of the massive hole there in with inventory down the line. Disney already has the DVC members’ “hotel” money; they only gain any auxiliary expenditures. Yes, Disney could make some money from merchandise sales and dining, but without the parks open, they’d have to also limit what shops and restaurants are open at the resorts as well (like they did at Shanghai).
The other added complication is that for most of the DVC “resorts,” they’d also need to open “cash”-side hotel facilities, which house the feature pools, dining, shopping, and even check-in facilities in some cases. That just adds to the cost. At that point, why not just open up the hotel side for “cash guests?” Except that even just the same proportion of “cash” guests are not likely to go down to WDW for a resort-only stay. Either way, it’s not necessarily a given that Disney would be making any more money than they are now with the added operating costs.
I think we might see the DVC resorts (and perhaps their corresponding “cash” sides) come online before the parks, but I think we’re talking about weeks before a park opens, not months.