Joseph Gordon-Levitt will be in Sin City 2, not Godzilla or Guardians Of The Galaxy or whatever else you've heard 

After being considered to star in both that upcoming Godzilla reboot and Marvel's Guardians Of The Galaxy, Joseph Gordon-Levitt has turned down both potential franchises that he was definitely seriously in the running for, and not just as a means of leveraging that rumored then quickly denied deal to launch the new era of Batman in the Justice League movie. He has, however, said a definitive "yes" to starring in the upcoming Sin City: A Dame To Kill For, the Robert Rodriguez and Frank Miller co-directed sequel about dames and how they're always making you kill for them, am I right fellas? Gordon-Levitt will be taking on a role originally intended for Johnny Depp—so much so that the character's name was actually "Johnny"—until Depp was informed that the film was not based on an old TV show and got a look at the hat budget. Anyway, it's already January 8 and Joseph Gordon-Levitt only has one confirmed movie in the works, whereas last year he had like five, so basically he's retiring.