I don’t think WB is ready or interested in tackling another Justice League film. Whatever their assessment of JL’s failure, they certainly think the issue was in trying to bring these characters together at all (which they ONLY did because Marvel did so in 2012). It’ll be a while.
With the disjointed way they are handling Batman, Aquaman and Wonder Woman especially, and with relatively few JL member solo films set to happen, I just don’t see one happening anymore. Aquaman and WW are going to get trilogies, but likely nothing more by that point. Reeves’ version of Batman is going to be effectively standalone much like Nolan’s. And it’s still up in the air whether Superman, Flash and Green Lantern will happen (though GL is more likely?).
The only way it happens is if Wan, Sandberg or Jenkins propose a plan to put their characters together in a film. I don’t think that’s very likely. At this stage, if a JL film happens, it’ll would likely be set in its own continuity much like JL: Mortal was going to be, with a director who is dying to make it. No one is going to line up these days to tackle a team-up film like that.