Wonder Woman 1984 introduced a character named Asteria, a legendary Amazon warrior whose powerful winged suit of armor was used by Wonder Woman during the film's climax. She was only mentioned as she was presumed to be gone until the post-credits scene where it was revealed that she is still alive living in the human world and played by Lynda Carter, who played Woman Woman in the 70s show.
After the sequel was released, it was reported (and now recently confirmed) that a third Wonder Woman film is in the works with star Gal Gadot and director Patty Jenkins returning. Then, during the DC FanDome event last Saturday, it was also confirmed that Carter will be returning in the role of Asteria and presumably have a bigger role this time around.
Jenkins teased a little bit about the film during the event. She said, "Gal, who's so bummed not to be here, who's the busiest person in the world, with now three little kids and shooting, so she was so bummed not to be able to be here. But we are all three very excited about some exciting things coming up with Wonder Woman 3."
At first, it may be surprising that Carter will be returning in the third film since you can interpret the post-credits scene as just an easter egg nod to the actress, who is the OG Wonder Woman from the beloved 70s show. But then the purpose of a post-credits scene is to tease what's about to come in the next film. Besides, Asteria is alive and well so why not have her be part of the action in Wonder Woman 3. It's going to be awesome to see Gadot and Carter work together and it will be definitely a must-see for fans.
As of now, there's no release date for Wonder Woman 3 as it is still believed to be in early development. It may take some time before it hits the screen since Jenkins is also working on the Star Wars film Rogue Squadron and a Cleopatra film that will also star Gadot.