It looks as though the next mission-based DLC for Saints Row: The Third is called Trouble With Clones and it will run you 560 MS Points, if the Achievements posted over on Xbox360Achievements.org are any indication.
According to the listing, the DLC will include 10 Achievements and 100 points, and it sounds like you will also be able to shoot bees at people with it, as well as use something called the Saints Flow fireball.
Also, an Amazon listing pointed out by G4 notes the DLC will see players helping Saints Row’s “biggest fan, Jimmy Torbitson, stop his Saints clone from terrorizing the city by using the new Bee Gun and unlocking the true power in Saints Flow. In the end, maybe even save a lost friend in the process.”
Amazon didn’t list a date for the DLC, neither did Xbox360Achievements.