Presently, putting extra value in blockbuster superhero movies is the name of the game. Next year, Wolverine will pop up in "X-Men: Apocalypse," "Batman v Superman: Dawn Of Justice" will find the titular characters joined by even more of the DC Comics roster, while "Captain America: Civil War" will feature every character in Marvel‘s Avengers stable (barring Thor and the Hulk), as well as Spidey, on loan from Sony. So of course the planned solo Batman movie won’t just find Ben Affleck brooding alone.
Latino Review reports that Will Smith might reprise his role as Deadshot from "Suicide Squad" in the as yet unnamed Batman film. That alone is probably too good a proposition to pass up for Warner Bros. But this is only a rumor, it might not happen at all, and I’d presume that if Affleck directs that he’ll want some input into the story.