This interview on MediaVillage.com with Showtime President Robert Greenblatt discusses the possibility for Sleeper Cell returning: link
EM: The second Sleeper Cell miniseries left the storyline open-ended. Is there any chance that you might find a way to wrap it up, maybe with a movie?
BG: We've talked about maybe in a year or so revisiting it and doing another installment of it, like they do with Prime Suspect. Every few years [Helen Mirren] comes back to do another installment.