Yes, What People are Teasing is a Superman Credits Scene in Black Adam
Since people are teasing it on Twitter I’ll just put it out there: there is a credits scene with a cameo by Cavill as Superman in Black Adam.
The scene in the TV spot of the Rock saying “There’s no one on this planet that can stop me” is from a credits scene where he’s talking to Amanda Waller. You hear Cavill say “Good thing I’m not from this planet” as he steps out of the shadows into the camera. That’s it.