I too will be sad when she finally quits but I don't think (and certainly hope) it won't be any time soon. From watching the latest videos, it is clear that she and her husband are having a great time making them and while that's the case and it brings in good money, why would they stop?
Personally I think she might do a few fully nude (Playboy style) pics/videos but that will be as far as she goes. She has made a lot of money keeping us all on tenterhooks these last few years and good luck to her.