One of the first measures Walt Disney World implemented for reopening last July to help with capacity was a park reservation system, which requires guests to reserve their spot at a specific park per day ahead of their trip. Parks Pass availability is distributed with varying availability among ticket holders, Annual Passholders, and on-property Disney Resort guests.
And though this system may make planning last-minute trips during busy periods or changing plans a bit more challenging then it was previously, it looks like this park reservation system will be around for some time still, as Disney has opened 2022 theme park reservation bookings, and has extended their parks pass calendar until January 2023, implying that this system will be used for at least the next two years.
Though we don't know about 2022 yet, it has been confirmed that enhanced health and safety measures will remain in effect for the remainder of 2021, including face coverings required for all guests ages two and up.
As a reminder, under current policy guests with the Park Hopper add-on must make a Disney Park Pass reservation for the first park they plan to visit AND enter that first park, and can then "hop" to any park they want to without a reservation. You can check out current Disney Parks Pass availability on Disney's official website here.