The back and the forth is apparently over as The Rock has announced, via Twitter, that he is Black Adam.
Black Adam is the original Shazam! - the son of Pharaoh Ramses II, Teth-Adam was given powers by the wizard Shazam (so many Shazams) and for centuries was Egypt's protector. But he went astray and became evil; eventually Shazam stripped him of his powers. But he got them back centuries later when Billy Batson got the power, and the two became arch-enemies. Black Adam has fiipped between good and bad, and has done such morally murky things as killing every single man, woman and child in the fictional nation of Bialya. You know, morally murky stuff like genocide!
I doubt that The Rock's version of Black Adam will be genocidal. I imagine this is going to be the anti-hero version of Black Adam, the protector gone astray who, after battling Billy Batson in a Shazam! movie, decides to try his hand at being a hero again. Especially since The Rock tagged his announcement with #TheAntiHero.
Supposedly The Rock was going to announce this at Comic-Con, so I have to imagine some kind of behind-the-scenes movement is happening on the film, and that we're about to have it officially announced. Maybe Warner Bros is about to give us some official word on that slate of Unnamed DC Movies.