Shazam is interesting because his rights are actually owned by New Line Cinema, which is owned by Warner Bros. Therefore, they will be the ones producing the futures Shazam movie, not Warner Bros. However, it is widely believed based on many people's talking that it will still take place in the DCEU. With that said, yes, The Rock has been cast as Black Adam for years now and based on talking, it seems there will actually be a Black Adam movie prior to a Shazam movie where essentially the villain gets introduced first. Then, just recently, you are right that The Rock has hinted that now the Black Adam will actually initially appear in some movie even prior to his own movie, but he is keeping which movie that is a secret. Anyway, all this just adds to the rumor production mill that is WB, where they announce a bazillion future movies with no timelines, then struggle to get productions even started, and then as a reaction to everything, constantly change what direction they are heading and what they want to do. Thus, we always have to take ALL these future movies with a grain of salt because you never know when WB will change their mind. Shoot, for all the movies they have announced, with every day that passes, the likelihood of us even seeing two DCEU movies in 2018 is slim. Literally, the only movies that are in production right now are Wonder Woman, Justice League, and Aquaman. The others they can't get off the ground.