We sort of thought we knew this for a long time, but there was never confirmation, then before DC announced anything, Dwayne Johnson jumped the gun and suggested he was deciding whether to be Shazam or Black Adam, but today he actually came out and said it. He's the bad guy.
Or, in his words, "#TheAntiHero."
Some have been reading into that phrase, suggesting that he won't be all bad - a fair assumption, given that he's only really ever played an out and out villain on WWE TV. Though when I read it, the only sense I get is that he's embracing the character's point of view.
Now then - who could play a suitable Shazam to take him on? (Please not John Cena.)