I am so bored that I started crunching numbers...There are just over 30,000 hotel rooms on WDW property. However, assuming that values and moderates remain closed, there are approximately 5,000 DVC villas and 409 FW Cabins. So, that's about 5500 rooms. Let's say the average # of guests per "room" is 4, so that's about 21,600 on-property guests (plus the campground?) if they are all occupied.
If the deluxe resorts that DVC are attached to all open then the number of "rooms/villas" goes up to 10,762. Assuming again, that average family size of 4, you're still under 50,000 on property.
Assuming that values and moderates stay closed, even with EVERY other room on property occupied and every guest has tickets, its still under 50,000 guests on property. If on property guests are given first dibs on park reservations, I just can't see how they wouldn't be able to get into a park.