Dwayne Johnson Teases That He Might Be In A DC Comics Movie

Yesterday, Dwayne Johnson (aka The Rock) tweeted this vague response, igniting rumors that Johnson is in talks or cast in an upcoming DC Comics movie adaptation. Many fans responded to The Rock's tease, but got no response. So what might The Rock have up his sleeves? Could there be a Warner Bros/DC Comics movie in the works? Or is The Rock just trying to get his fans talking (sometimes a lot of nonsensical buzz can turn into reality).

I remember back in 2007 that Johnson was attached to play Black Adam in a big screen adaptation of the Captain Marvel comic book Shazam!. Somewhere along the line, that project fell off the board. Has the project been rekindled? Or more likely, is Johnson in talks for another DC Comics property? If so which one?