Although Shazam! will feature a variety of characters from the comic book mythos -- the Shazam family evidently being among them -- it will not feature Billy Batson's classic nemesis from the comics, Black Adam.
Despite the main antagonist of the film established as being Dr. Thaddeus Sivana, with a Black Adam spinoff currently in development, many fans understandably expected the character to appear somewhere in the film, such as the post-credits sequence, which most contemporary superhero films tend to use to introduce new characters or events as they expand their respective shared universes. However, confirmation that Dwayne "The Rock" Johnson would not appear in the film came from a Q&A session with director David F. Sandberg and producer Peter Safran.
When asked about a rumor that Johnson was available for a post-credits cameo but was kept from appearing due to the absence of a costume, Safran answered, "Complete myth. Everything about that - no, he might've been available. That's the only thing about that statement that might be true. I don't know if he was or not. But, no, there was never a conversation with him about a post-credits sequence. Truly, never."
What this means is we're not likely to see Johnson's Black Adam before the solo film is released in the future, likely later than 2021, judging from the DCEU's current release schedule. In fact, few details have been released regarding Black Adam, except that Johnson will be starring in and producing the film, which he has been attached to since the early 2000s before the DCEU was established.
Although Black Adam was originally intended to debut in Shazam!, a decision was made to exclude the character and replace him with Dr. Sivana. Considering Black Adam is very much an antihero, it's understandable that Warner Bros. would refrain from introducing the character in the role of a villain in order to avoid complicating the plot. Especially since, according to Johnson, Black Adam will be very different in tone than Shazam!.
Directed by David F. Sandberg, Shazam! stars Asher Angel as Billy Batson, Zachary Levi as Shazam, Mark Strong as Dr. Thaddeus Sivana, Djimon Hounsou as the ancient wizard Shazam, Grace Fulton as Mary Bromfield, Jack Dylan Grazer as Frederick “Freddy” Freeman, Ian Chen as Eugene Choi, Jovan Armand as Pedro Peña, Faithe Herman as Darla Dudley, Cooper Andrews as Victor Vásquez and Marta Milans as Rosa Vásquez. The film arrives April 5.
(via Screen Rant)