I could see tons of parks moving to that just in general for the future .. a lot of tourist attractions do that already by giving you a discount if you get a specific day (or sometimes time) ticket in advance. I know
Legoland Discovery Center in Atlanta was like that.
Probably won't be hard for parks to implement (wouldn't be hard for Disney, you'd think) and will just let them keep control of capacity a lot easier than turning people away at the door. Better ot be disappointed at home when trying to buy a ticket rather than at the front gates.
Unfortunately that just makes another "pain" to planning and reducing flexibility even more (if they keep it beyond this pandemic).