Given as Whedon's Justice League was more or less attempting to tie Keatonman and Reeveman to Batfleck and Supercavill via both using the old musical cues, Cavill Supes suddenly spouting corny dad jokes and Alfred alluding to Batman Returns (and perhaps even the Adam West show) with the" Exploding penguins "line. I can totally see Warners just outright merging Supes and Bats and saying that the Donner films, the Burton films and some of the Snyderverse stuff happened as a quasi interconnected continuity and now we are moving on from all of it.
That way we have a mostly retired as Batman but still active as a mentor Bruce Wayne in the persona of Keaton who seems eager to be Bruce again even if Affleck or Bale don't seem to want to.
Meanwhile we get a Shrodingers Superman situation with a Seminretired Superman still out there somewhere in the universe, ready to be used as cameo fodder whether Cavill plays the role or they hire someone else (Brandon Routh,perhaps?) to pop in from time to time if they need a jobber or mentor figure to say Kara or,yes, set up Jon Kent at some point. They can essentially use Superman without having to show him. Think the first season of SUPERGIRL. He's there,just off camera,just out of frame.
Or,if Dwayne Johnson wants to use a Superman in his Black Adam corner of things, he can use Cavill or someone else without necessarily stepping on the Snyderverse's toes or having to align with the larger DCEU.