They could also limit the number of hotel rooms booking, if they go with a crowd control approach. Magic Kingdom alone has an average daily attendance of 52,000 people. Assuming 2-4 guests per room, even 90,000 hotel guests would represent lower than average crowds when spread over four theme parks.
True social distancing is all but impossible, no doubt about that, but smaller crowds in general could still be a goal.
Passholders supplement tourists, but I'm sure Disney wants the big dollars the out of town guests bring in.