As you can see here, Aquaman and the Lost Kingdom had added three new cast members and a returning cast member.
Indya Moore will appear as Karshon, Jani Zhao will appear as Stingray and Vincent Regan as King Atlan, a role previously portrayed by Julian Lewis Jones in Justice League and Zack Snyder's Justice League and by Graham McTavish in Aquaman.
Announced to be returning is Randall Park as Dr. Stephen Shin. Also, here, you can see a few small details that Jason Momoa has shared about the film.
The film is expected to be released on December 16, 2022. More information will possibly be revealed at DC FanDome 2021, which will begin on October 16, 2021 at 10:00 A.M. Pacific Time.