SeaWorld San Antonio and the two Texas Six Flags parks will continue to limit capacity and require face masks.
Cedar Fair says it will fill 45,000 seasonal positions across its parks for the 2021 season.
The park will be taken over by Herschend Family Entertainment, the company behind Dollywood and Silver Dollar City.
Several parks' reopening dates depend on government COVID-19 guidelines.
Six Flags Magic Mountain and Legoland California both announced new, ride-less events Thursday.
The theme park chain lost $590 million in 2020, but expects 2021 to be an improvement.
Six Flags America and California's Great America are helping facilitate COVID-19 vaccine distributions.
SeaWorld San Diego can reopen as a zoo now that California's stay-at-home order has been lifted.