According to cast members at the park, Disneyland will reopen Main Street U.S.A. (from the entrance up to Sleeping Beauty Castle) with limited capacity, in the same fashion as Buena Vista Street has operated at Disney California Adventure as of late. This would mean shops and restaurants will open up and down the iconic avenue. The rumored date for the reopening of Main Street U.S.A. is March 14th, 2021, which aligns with the plans for DCA, and just happens to be one year to the day since Disneyland closed.
With Main Street reopening, this would allow Disney to close all of California Adventure to guests not attending the ticketed dining and live entertainment event at Disney California Adventure, while still offering a similar lineup of offerings to what they have for guests now.
Disney has yet to announce the reopening, but cast members have started getting their calls today to return to work on Main Street U.S.A.