So even if this information about Black Adam being the primary antagonist in Man of Steel 2 isn’t true, don’t be surprised if he does go mano a mano with Superman at some point or merely cameos during the tale.
All this being said, Black Adam showing up in Man of Steel 2 is actually plausible.
For two years, Dwayne Johnson has been talking about how his Black Adam will eventually fight Superman, although it’s never been specified where that would take place.
Then last December, Johnson posted a photo of him with Henry Cavill, teasing that these two might be doing something together.