A lot of people are pissed off about the ending, but I actually liked it. It was kind of appropriate, considering what kind of story they've been telling for the last eight years. Without dropping spoilers, I'll just say that it seems perfectly obvious what happened...I think people are only mad because they wanted all the gory details.
I dunno about a movie, it's possible but the star (wtf is his name, I'm too lazy to look it up) has been wanting to leave the show for years and only stuck around for contractual obligations. With enough cash though they might be able to entice him back for a follow-up.