There is just one shared universe continuity. Robert Pattinson's Batman joins the existing continuity after his trilogy completes. If Henry Cavill is replaced, it seems most likely that a brand new Superman will also join the continuity. (This probably means pretending that MoS, BvS, and JL never happened, since these will be brand new versions of the former characters versus simply recasting the same version.) If Henry Cavill continues, the universe will likely still proceed as is if BvS and JL never occurred, i.e., those films simply aren't referenced moving forward.

Over the next 8 years Pattinson's Batman will launch a new separate continuity as the existing one winds down. Reeves' Batman trilogy stands alone; however new superheroes are introduced in solo films that will eventually interact with Battinson in this new continuity. Reeves' trilogy completes in 2026. The first film in which Battinson and other characters cross over will therefore be 2028. (Pattinson is then 42, but about 40 when filming.) 2028 will be the true launch of that new shared universe. Henry Cavill continues as Superman with at least two solo films. From now until 2028 Wonder Woman, Aquaman, Flash, Harley Quinn, Shazam, and Black Adam wind up their respective character arcs. In 2028 the existing universe concludes with Flashpoint as it's grand finale. Either 1) Affleck returns for at least one JL film to complete the Snyder arc and cameo at the end of Flashpoint, or 2) the Batfleck character is recast.