Recasting and rebooting Superman was inevitable
After the disaster of 2017 Justice League.
In no reality was Cavill coming back, his cameo in Black Adam was due to The Rock's ego, the embarrassment that Cavill faced could've been avoided if the studio didn't allow The Rock to dictate who he should be facing off on screen.
Realistically can an actor play the same character over and over again? playing a character like Superman is an extensive part of your life, it's ten years out of a thirty year work life, so you just spent 10% of your work life on three productions.