The New Gods Movie/Justice League Odyssey Crossover
Even with the Justice League movie avoiding Darkseid despite Zack Snyder's original script, adapting Justice League Odyssey to film seems to check multiple boxes off the DCEU's to-do list. And wouldn't you know it, a DC movie already being developed could help make some of the same introductions Snyder was hoping to with Justice League...
From these details alone, casual fans can appreciate how well the Odyssey comic resonates with the forces and faces already alluded to in DCEU films. Introduce a new Green Lantern actor or actress, along with a mission calling on existing heroes of Earth? Check. Connect to a larger Green Lantern Corps active in the DCEU (assuming that movie is still being made)? Check. Shift focus from the Darkseid that might have been in Justice League by introducing an even bigger threat on the way? Check.
With Ava DuVernay making a New Gods movie, that film could provide a perfect launching point to link the Justice League to the cosmic side of the DC Universe (hopefully still based on Cyborg's Mother Box metamorphosis). If Warner Bros. chooses, these separate movies could also set the stage for a battle or crisis calling on their biggest heroes. For many, the Justice League event movie DC has yet to deliver.
Justice League 2: The Classic Heroes, Villains & All
Finally, the tried and true Justice League heroes and villains are continuing their new adventures in the mainline Justice League series. Despite the different media, there will always be value to the core "Justice League" brand in particular, just like Marvel's Avengers. Exactly what story that sequel would tell... well, that's up to the studio. For all the Justice League controversy that took place after the movie was filmed, those events can and should remain canon. Not a problem, since the final scenes of the movie - just like the new Justice League #1 - wipe the slate clean for a fresh start. From which the studio's new leadership can take any number of options.
A direct sequel to Justice League's post-credits tease of Lex Luthor and Deathstroke? An ensemble story built towards by the heroes' solo films? Fallout from Flashpoint? Or possibly even a sequel stemming from a new Superman movie, with a Batman who may or may not be Ben Affleck. If the spinoffs succeed as well as they could, then whatever Justice League movie the studio chooses can make a strong statement about the vision for the DCEU's future.
A vision that, to this point, even those leading it seem to disagree on. If that isn't solved first... then giving room for these heroes to gather to their strengths may not be a bad idea.