After returning in The Flash for what seemed to be his last time, Ben Affleck's Batman will also appear in Aquaman and the Lost Kingdom, raising the question of why the DCU can’t let fully go of Affleck’s version of the character. Following a Jason Momoa cryptic Instagram post featuring Ben Affleck on the set for Aquaman 2, it was reported Affleck would indeed appear as Batman in the Aquaman sequel. However, with James Gunn taking over the mantle of the DCU, nothing is for sure outside the movie's releases. Affleck's appearance in Aquaman 2 is not even certain now.
https://screenrant.com/why-ben-affleck-is-still-batman-in-dceu/