No he didn't. He said that season 7 will be their last, which was a typo; he meant season 8. Season 8 for Regular Show is scheduled to air later this year. They're ending it on their own terms, why do you think made a cake celebrating their run? Just because a show discontinued the release of new episodes, does not mean it is cancelled.
I didn´t know about the cake, but no matter cancelled or just ended, the point is that this show will finish soon, so let´s enjoy the rest of the 8 season and remember this as one of the best cartoons in cn