The Guardians filmmaker is currently gearing up for Peacemaker Season 2, which will help expand the DCU. The first movie Superman featured a number of other heroes, but it's unclear what the plan is for Aquaman. While on the Peacemaker podcast, Gunn was asked about about the character formerly played by Jason Momoa, and he said:

DC Studios' James Gunn has just revealed Aquaman's status in the new DCU. In the newly rebooted cinematic universe, Creature Commandos and Superman are the only projects that are fully 100% DCU canon (so far).

There’s a new DC universe in town that’s being kick-started by James Gunn’s “Superman” this weekend. Headlined by David Corenswet as the Man of Steel, “Superman” is poised to relaunch the DC universe and usher in a more vibrant, less serious connected world after Zack Snyder’s “Man of Steel” and the resulting DCEU.