It's possible that Ben Affleck, Zack Snyder and the cast of the Justice League will show up Saturday at Comic-Con as a surprise during WB's big Hall H presentation.
The last couple of years has seen WB show up big time at Comic-Con, which included Batman Vs. Superman and Suicide Squad last year in addition to the reveal of DCEU concept art. Previous to that saw the DC Trinity appear for the first time with Ben Affleck, Henry Cavill and Gal Gadot on stage revealing a first look at Wonder Woman. The prior year saw Zack Snyder make the announcement for Batman Vs. Superman.
In THR's report on WB's presence at Comic-Con, they speculate the Justice League will show up as well, noting, "...it's hard to imagine there won't be a surprise appearance by the Justice League cast and a splashy sizzle reel from the film to accompany them."
With Marvel Studios appearing this year (they skipped out on Comic-Con last year) bringing Guardians of the Galaxy 2, Doctor Strange and Black Panther (possibly more with Captain Marvel speculated), it's probably safe to assume DC will answer with the Justice League cast.
WB's Hall H presentation with the confirmed cast of Wonder Woman and Suicide Squad takes place Saturday, July 23, beginning at 11:30 a.m.
"Justice League" has a November 17, 2017 release directed by Zack Snyder starring Ben Affleck as Batman, Henry Cavill as Superman, Gal Gadot as Wonder Woman, Jason Momoa as Aquaman, Ezra Miller as The Flash, Ray Fisher as Cyborg, J.K. Simmons as Commissioner Gordon and Willem Dafoe as an Atlantean.