I always thought that was a possibility for Disney too. Not in July but come Sept if demand is still way down they could stagger one park closed each weekday Mon-Thur. Keep all 4 open on the weekends. It makes a lot of sense operationally.
Universal could close IOA on Mon/Wed and Studios on Tue/Thur. You theoretically cut pure park operating costs in half and still have enough capacity to meet demand. You lose some revenue on muti-park tickets and would have to either close the train or maybe just make it round trip. Or they could keep Potterlands open in both parks all the time and just rope off the exits out of the lands. If Studios park is closed the only way to get to Diagon Alley would be by HE. Sorta like the train at AK to conservation station minus the smelly animals