It seems the reason why there has been no Hulk film since 2008 is because Marvel doesn’t have the necessary rights to produce one. In an interview with Collider where he discussed how many films are left in his contract, Mark Ruffalo stated that rights issues are preventing another standalone Hulk movie.
“As far as a Hulk movie, a standalone Hulk movie, Marvel doesn’t really have the rights to that yet. That’s still Universal’s property, so there’s that issue. That’s a big impediment to moving forward with that, now I don’t think that’s insurmountable, by the way, but I don’t know where it’s going from here for me.”
Ruffalo was also asked if he appears in Captain America: Civil War: “I don’t know if I’m in it yet. I don’t know. Sometimes these things happen at the last minute in this world. I really don’t know where I fit in from here on out, and I’m not sure they do.”
Avengers: Age of Ultron is set for release in the UK on April 23rd and North America on May 1st, with Joss Whedon directing a cast that includes Robert Downey Jr. (Iron Man), Chris Evans (Captain America), Chris Hemsworth (Thor), Scarlett Johansson (Black Widow), Mark Ruffalo (The Incredible Hulk), Jeremy Renner (Hawkeye), Don Cheadle (War Machine), Cobie Smulders (Maria Hill), Samuel L. Jackson (Nick Fury), Paul Bettany (JARVIS / The Vision), Aaron Taylor-Johnson (Quicksilver), Elizabeth Olsen (Scarlet Witch), Hayley Atwell (Peggy Carter), Idris Elba (Heimdall), Anthony Mackie (Falcon), Tom Hiddleston (Loki), James Spader (Ultron), Stellen Skarsgard (Erik Selvig), Thomas Kretschmann (Baron Strucker), Josh Brolin (Thanos), Claudia Kim (Dr. Cho), Andy Serkis (Uylsses Klaw), Henry Goodman (Dr. List), Julie Delpy (Madame B) and Linda Cardellini (Laura Barton).