I think a month of seeing how Universal is doing will also give Disney good indications what they need to do come July 11th.
People could come out in droves, there is good news about the virus, and Universal, Sea World and
LegoLand are booming being the only big theme parks in town open. Disney could then decide to open with a lot less restrictions.
OR
People are still afraid to go out, can't (or don't want) to travel to Orlando for a "vacation" during this time and instead opt for RVs, camping, beaches and Universal looks like a ghost town. Disney can then plan and staff accordingly.
It's a crazy time for sure. I feel for the cast members that may still be out of a job even when WDW opens up.