After hinting broadly that he would have a part in a DC Comics-based Shazam movie (see "Dwayne Johnson Confirms 'Shazam'"), Dwayne "The Rock" Johnson went on Twitter to confirm that the role he will play in the film will be that of Black Adam, tweeting "Kneel at his feet or get crushed by his boot.  My honor to become #Black Adam."
Created by Otto Binder and C.C. Beck in 1945 for the Captain Marvel comic book, Black Adam was an ancient Egyptian predecessor of Captain Marvel, who served as the comic’s primary villain.  In the 21st Century DC Comics, which acquired the rights to Captain Marvel in a lawsuit and changed the comic’s name to Shazam, has softened Black Adam’s villainy a bit, making him  more of the misunderstood antihero, and giving the character unprecedented visibility in the post-New 52 DC Universe.
Meanwhile Variety not only confirms Johnson’s role as Black Adam, it reports that Darren Lemke (Jack the Giant Slayer, Goosebumps, Shrek Forever After) has been hired to write the screenplay for the new Shazam-based film.  So far Warner Bros. has not confirmed pre-production work on a Shazam movie, nor has Warners set a release date for the film, though the studio has reserved nine premiere dates between 2016-2020 for as yet unspecified movies (see "Batman Blinks").