Pretty sure James Gunn was told not to recast Deadshot so he changed Elba’s character last minute. All because of the possibility of Will Smith returning. Also, Margot Robbie/Cathy Yan were told to ditch Penguin because of Reeves, so they went with Black Mask (which tells you Reeves has no immediate plans for Roman). And they couldn’t use Batgirl because of her solo film. So I’m guessing Reeves may have been told not to use Harley Quinn, Batgirl or Deadshot. Sounds like everyone works together behind the scenes. Gotham City Sirens was probably cancelled because of Reeves’ Catwoman plans. Joker is obviously the big exception to each universe. So I don’t think Deadshot will show up. Personally I think hitmen/assassins are over-used in action movies especially with John Wick still going strong. Two-Face however (and his gang) could give Batman a fight.