Park Hopper tickets will be returning to Walt Disney World starting on January 1, 2021, with modifications to the original ticketing option to support COVID-19 precautions.
Under the modified park hopper option, guests will need to make a reservation for their first theme park and physically enter that theme park. You will then need to confirm your park hopper (which presumably means your intention to park hop that day). Starting at a designated time (it is officially stated to be at 2:00 but may change based on the day and park), guests will be allowed to park hop, subject to park capacity limitations.
Whether this is going to be worthwhile remains to be seen (for instance, you may be able to park hop to Animal Kingdom, but capacity limits may make it next to impossible to park hop to Hollywood Studios), but for those who want to spend a day at a park and then head over to EPCOT for dinner, it opens the door to do that.
UPDATE: In order to ride on Rise of the Resistance, you will need a park reservation for Disney's Hollywood Studios, essentially making it impossible for those who park hop into DHS to ride.