BEVERLY HILLS -- "Dexter," far and away the biggest hit on Showtime and a signature cable series (despite what you may have thought of the sixth season), could extend beyond the eighth season. That's the season that most reasonable observers, not to mention star Michael C. Hall, expect to be its last. But Showtime boss David Nevins said on Monday, "I'd be stupid if I didn't leave the door open" for a ninth season. Hall -- whose Dex has now been revealed to sis Deb as a serial killer -- said this afternoon that the expectation is that the eighth will be the last season. "I think the sense is, we're moving towards a definitive end." But he then left that aforementioned door ajar as well: "Never say never..." The seventh season starts Sept. 30. Check out a trailer below.