The IMDB page of "Shazam" only has a single confirmed actor and he's not even playing the lead character.
Dwayne "The Rock" Johnson was rumored to be the main protagonist in the film "Shazam" set for 2019 release. However, he later chose to play the antagonist Black Adam because he thinks the character is more interesting since he rose from a slave to hero and eventually the anti-hero, according to Digital Spy.
There are rumors who could play the main character but since the film is set for release in 2019, there is no need to confirm who will play the uniquely powerful hero.
But it is important to note that DC is not just planning to release individual movies. Taking a cue from the highly successful Avengers and their individual movies, DC will also focus their efforts on the legendary "Justice League" which will feature some of the greatest superheroes ever.
According to Inverse, Geoff Johns and "Clerks" director Kevin Smith hosted "DC Films Presents: Dawn of the Justice League" which was aired in CW a few weeks back which reveals their plans for multiple movies on individual characters leading up to the Justice League film.
From the standpoint of creating a movie dedicated to Justice League, it would be unwise for DC to just ignore other characters. Yes, Marvel Universe is extremely expansive but DC Universe doesn't fall behind when it comes to coming up with interesting characters and among those characters are Shazam and Black Adam.
Fortunately, the men behind the adaptation of DC Universe has acknowledged the importance of expanding the said universe and characters. In a separate report by Digital Spy, Dwayne Johnson indicated that he's open to appearing in DC movies as Black Adam even before the official release of the film.
If he ever gets to be part of any of the upcoming movies, the floodgates will definitely open for more heroes. After all, CW has been very successful in adapting the heroes of DC to the small screen with a series of crossovers.
