Schedule Slip: Of 9 months from June 2012 to March 2013, so the film could be converted to 3D & more scenes could be shot with Channing Tatum, after the main complaints from test screenings were that the film wasn't going to be in 3D and audiences weren't happy with how little time was spent on the development of the friendship between Duke and Roadblock before Duke's death. It was also announced a month before the films release, and roughly a week before the toys were due to be released.
Troubled Production: As noted below, the movie's highly-anticipated release was delayed, almost at the last moment, by nine months, for reshoots, ostensibly to make a 3-D version possible and boost interest in international markets (and, unofficially, to avoid competing with Magic Mike, also starring Tatum).
This wouldn't have been so much of a problem had Paramount not been heavily promoting the original June release date up to the point they put it off, leaving them with just two movies on their summer calendar. Left in the lurch in the meantime was an entire line of toys based on the movie that Hasbro was bringing out.
The effort to "boost interest in international markets" notwithstanding, the film was still banned in Pakistan due to its negative portrayal of that country.
What Could Have Been: The movie was originally slated for release in 2012, but was held back a year to do some reshoots with Channing Tatum, expanding Duke's role in the film. Carrie Vaughn suggests this expansion must have come at the cost of other scenes (such as a possible reaction shot from the British Prime Minister when London was destroyed or any characterization for Flint at all) which had to be cut to stay at a 110-minute running time.
An extended cut was made available for Blu-Ray the day of release as an exclusive to Best Buy (in the US), extending the running time by twelve minutes. Whether it's an improvement is up for debate, but Flint does get a bit more characterization.