MIB3, which is yet another 3d movie is scheduled to be released May 25, 2012. Only a few details about the film's plot have been confirmed though the film will have a time travel plot with Agent J having to go back in time to 1969 to visit a young Agent K. The film's villain, Boris, travels back in time to try to kill Agent K in order to set off a chain of events which will result in the end of the world.
Check out some footage from the upcoming film.