Justice League: 10 New Details Revealed By Director Zack Snyder
1. Could The Joker Make A Surprise Appearance?
This one could be a stretch, but the groundwork has definitely been laid. As you may recall, Batman v Superman: Dawn of Justice featured Bruce Wayne looking up at a fallen Robin's defaced costume ("Hahaha, joke's on you Batman"). It was clearly The Joker who had done that, and Suicide Squad later confirmed that the Clown Prince of Crime murdered the Boy Wonder.
Snyder, meanwhile, would tell fans that this was the Dick Grayson version of Robin, and it really did feel like the filmmaker was building to...something.
Whether that something was supposed to be addressed in The Batman, the original version of Suicide Squad, or even Justice League is hard to say, but Snyder has revealed that he was a big fan of Jared Leto's interpretation of The Joker, so it seems possible that he could factor into this story in some way, shape or form, even if it's just a vision or some sort of flashback to the Dark Knight's past...