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:

Some of the initial guesses for the heroes in the Hall of Justice metahuman mural in Superman were spot on, while others were way off.

While going over the first episode of Peacemaker, DC Studios co-head James Gunn clarifies whether or not Aquaman is canon in the DCU.