It's a shame, really, because I'm so fond of the first two films in the franchise (the ones with the Wayans). But, yes, sadly, this franchise has sung its last tune -- the final nail has been hammered home. I don't expect Scary Movie 5 rake in no more than $50M. Now will that warrant another sequel? I hope not.
Have you had a chance to check SM5 out yet? What'd you think?