Batman v Superman: Dawn of Justice may have finally brought the Trinity together, but it was Justice League that finally introduced DC Comics' most famous superhero team to the silver screen. Batman, Wonder Woman, Aquaman, Flash and Cyborg came together to battle Steepnwolf and his Parademon minions, and Superman later joined them once he'd calmed down from being resurrected. These six now stand together as the ultimate line of defense against those who wish to destroy humanity.
When Bruce Wayne, Diana Prince and Alfred Pennyworth were inside Wayne Manor discussing how they would turn the gigantic house into the Justice League's headquarters, Diana mentioned that there would be "room for more" at the meeting table. Taking her foreshadowing into account, we've gathered some worthy candidates who should join the team, be it in Justice League 2 or another movie.
Green Lantern is typically a founding member of the Justice League in most stories, but aside from a few Lanterns participating in the battle against Steppenwolf thousands of years ago, the Justice League movie wasn't illuminated by the emerald light. The Green Lantern Corps will introduce Hal Jordan and John Stewart into the DCEU, and ideally that movie will explain why neither of them, nor one of their fellow Lanterns, showed up to help Earth's superheroes thwart Steppenwolf's second invasion. Regardless, whenever the Justice League opens their ranks, you wouldn't be foolish putting money on Green Lantern being one of the new recruits, if not the first one they approach. As for which human Green Lantern will join the team, Hal would be the likeliest candidate given that he helps form the team in the comics, but given that John Stewart was a founding Justice Leaguer in the Cartoon Network animated series, we shouldn't rule him out of the running.
Most kids dream of being a superhero, and in 2019, Billy Batson will have that dream fulfilled in the Shazam movie. Although Shazam (or Captain Marvel if you prefer) has teamed with most of the Justice Leaguers in the comics numerous times, it wasn't until post-Forever Evil in the New 52 that he finally became a regular member of the team, and even that tenure was relatively short-lived. Nevertheless, with Shazam being the next major superhero to be introduced to the DCEU, it stands to reason that when the cinematic Justice League starts to expand, the World's Mightiest Mortal will be put into consideration. However, it would be interesting to see if the heroes changed their tune upon learning that it's actually a 10-year-old who's been fighting the likes of Doctor Sivana.