We Already Have the First Look at Momoa's Aquaman
Batman v Superman: Dawn of Justice director Zack Snyder (who is also directing the Justice League films) tweeted out this image of Momoa as Aquaman in 2015. "Unite the Seven" refers to the members of the Justice League: Batman (Ben Affleck), Superman (Henry Cavill), Wonder Woman (Gal Gadot), Aquaman, Cyborg (Ray Fisher), the Flash (Ezra Miller), and . . . well, no one really knows. The seventh spot could belong to Mera, or it could be meant for one of the displaced founding members of the League, Green Lantern or Martian Manhunter.
If you did end up seeing Batman v Superman, then you also caught Aquaman's short cameo!