I think so. TF4 seems to have sold around 27-28 million tickets, which is around 10 million lower than TF3 which was already a good ways down from TF2. I could see TF5 falling to the low 20's, if not high teens. TF4 doesn't seem to have gotten a very good audience response when compared to the others.
Only way I'd buy a ticket at this point. (Just to see the trainwreck)