Prior to season 5, I think the ratings would have stayed the same. The writers were just running out of stories at that point. Personally, I'd like to see all series end at S5, if they even make it that far. Writers would be able to go out on top and could wrap up story lines and give characters proper endings. If the fanbase was huge, they could always bring it back for a limited series, like The X Files is currently doing, or try for the big screen, or even a reunion show. Just my .02.
"Awesome" ends in "Me".
I think not.