Since the Elseworlds concept will continue within DC Studios, there is always the possibility of having a Black Adam vs. Superman movie with Johnson and Cavill happen in the coming years. Once the DC Universe has gotten beyond their Chapter 1: “Gods and Monsters” slate, the studio could revisit the DCEU continuity as an Elseworlds movie, which can easily be a one-off without having to recommit to that timeline again. By that point, DC Studios will also likely have been able to experiment more with other Elseworlds stories to know how to best approach a Black Adam vs. Superman film.
Whether or not Cavill and Johnson are up for reprising their characters remains to be seen, as the two stars are moving on to other roles and projects. However, if pitched under the right circumstances, there is always the chance they would agree to finally duke it out as Black Adam and Superman. But for now, the world will have to wait and see if a proper Black Adam follow-up ever becomes a reality.