Everyone knows Nightwing as Batman's first sidekick, but he has not gotten the role fans feel he deserves. He has had small roles in films and shows. If you remember Batman: Under the Red Hood he was in those stories helping Batman track down Red Hood. He was mentioned in one episode of Teen Titans and he was the leader of Young Justice and he was a main character again in The New Batman Adventures and also his small role in the film Son of Batman but i feel he hasn't gotten the role he deserves. In Christopher Nolan's The Dark Knight Rises they hinted all over the film about who John Blake was going to become (Robin) but they never even mentioned Batgirl. But Richard John Grayson has never been mentioned in the Nolan franchise as a character that WOULD be added to the character list for any of his films.
Many people want DC comics to make a Nightwing film because fans feel he deserves one, his character has alot of good background that they could make into a very dramatic film that will allow people who have never even heard of Nightwing to walk out with a full head of knowledge of his origin, and of his life as a circus performer.
Now, who to play the Adult Wonder? Well here are some ideas.
Joseph Gordon Levitt. Many know he was basically Robin in The Dark Knight Rises due to the fact that Bruce gave him the coordinates to the Batcave and his name. They told you his name was Robin. So either they make a Robin film then a Nightwing film or just make a NIghtwing film.
Ian Somerhalder. Why? Because he just looks like Nightwing.
DC comics know that Nightwing deserves a proper film. His own role.