The Colbert Report happened. Stephen didn't have the time to put in to the show and Reducto and Phil Ken Sebben were characters that the show couldn't do without. Rather than go into death-spasms like Sealab did, 70/30 decided to end it and focus their attention on a new, untitled project. There are still 3 episodes left in the last season (Dunno why they're sitting on them) and that'll be all. Can't wait to see what their new project is, though...