5. Aquaman (2018)
Having already appeared in Batman v Superman: Dawn of Justice, Aquaman will appear in a movie of his own. That movie will see him return to the ocean to help his people combat a new threat - and that threat will most likely be Black Manta. It's unlikely that it will be an origin story, but it will surely touch upon the fact that he is half-human (on his father's side) and half-Atlantean (on his mother's side). Aquaman will probably have established himself as a member of human society over the course of many years, but this movie will probably see his people calling upon him for help as their very existence comes under threat from the aforementioned villain. Black Manta is a man called David (last name unknown) who had a chip on his shoulder because Aquaman had failed to save him from the pirates who enslaved him at sea (Aquaman hadn't actually seen him, but David felt as though he had been ignored). As a result, he put together a high-tech underwater battle suit and took vengeance on the ocean. The likelihood is he will kill some of Aquaman's Atlantean allies - possibly even some of his family - prompting the Justice League member back into the depths and into a final battle in which he will defeat the armoured rogue with the help of some of his aquatic friends (he can control sea creatures with his mind, after all).