The DCEU was in a state of flux even before DC Studios was formed, and shifting release dates plunged Aquaman and the Lost Kingdom into chaos.
The Flash was supposed to end with Michael Keaton's Batman being established as a Nick Fury-like figure, hence why he was lined up to appear in Batgirl and an eventual Batman Beyond project. It makes sense then that he shot a cameo role in the Aquaman sequel.
However, when the aforementioned release date shifts happened and The Flash was suddenly coming out after Arthur Curry's second solo adventure, Ben Affleck shot the same scene in Keaton's place.
We learned yesterday that neither actor will now appear in Aquaman and the Lost Kingdom due to James Gunn and Peter Safran not wanting to tease a future story that, simply put, probably isn't ever going to happen in the new DCU.
One scooper claims to have learned what the sequence entailed, revealing it would have featured Bruce "warning Arthur that something was poisoning the oceans setting up a future storyline." It's unclear what that storyline was or when it was going to be picked up on.
We'd assume Aquaman 3, though it may have also been a tie-in to Warner Bros.' scrapped Crisis on Infinite Earths movie. As things stand, we don't even know whether Jason Momoa will continue playing Arthur in the DCU as it's widely believed that he could swap the role for Lobo.
In Aquaman and the Lost Kingdom, when an ancient power is unleashed, Aquaman must forge an uneasy alliance with an unlikely ally to protect Atlantis, and the world, from irreversible devastation.
The movie stars Jason Momoa (Aquaman), Nicole Kidman (Atlanna), Patrick Wilson (Orm), Amber Heard (Mera), Yahya Adbdul-Mateen II (Black Manta), and Dolph Lundgren (King Nereus), along with newcomers in the form of Pilou Asbæk, Vincent Regan, and Indya Moore.
Aquaman and the Lost Kingdom arrives in theaters on December 20.