Re: Next Batman Villain?
Film 1: Victor Fries, somehow connected to Wayne Corp. Preferably as a tragic anti-hero. The Riddler in the background, trying to out-wit the worlds greatest detective.
Film 2: Mob-wars, The Penguin & Back Mask or something? Post-credit scene with a Joker-card.
Film 3: Harley & The Joker. Some fantastical enemies for spectacular action scenes? Croc or Clayface could always be tied in with the Joker, with him being behind their transformation(s) etc.