One thing we don’t know for sure is whether the non-Disney partner hotels are offered the same benefit as on property guests. Assuming they are not in the mix there are only about 24,000 Disney hotel rooms. I agree on the 4 per room for DVC. I would assume the average hotel room is closer to 3 people with some individuals, lots of couples and families of 3 mixed in with families of 4. Outside of the family suites it’s hard to sleep more than 4 to a room. So based on that math and half the rooms full that‘s 36,000 plus 18,000 for DVC or 54,000 total. If we assume a park capacity of 15,000 that gets you to 60,000 total capacity so plenty to spare. That also assumes nobody goes to Universal or Sea World or somewhere else off property or decides to spend the day golfing and/or at the pool and/or shopping at DS. In reality some portion of on property guests won’t go to a park each day.
On the DVC front the actual number of rooms used will be well under 4,500 for the first few months. Going on the tool today for the first month the 4 parks are open there is availability at every resort for either a studio or 1 BR villa for almost every day. Unheard of in years past. That doesn’t tell us how many rooms are available, but since they relaxed the use year expiration I think a lot of people have pushed back to the fall/winter in the hopes that some of the restrictions will be lifted or at least it will be less oppressive to wear a mask when the weather is less hot and humid. In other words while park capacity is at its lowest in the first few months after reopen DVC will not be at its usual 95% occupancy.
I used this list from touring plans to come up with number of rooms:
touringplans.com