maybe I'm wrong, but is there anything inherent in the RD that makes it a 8,9, or 10 speed? Wouldn't that just be a factor of the shifters and how much cable each shift pulls? i.e. a 10 speed shifter will pull slightly less cable than a 9 speed making the RD move just slightly less distance.

if that's the case I have a 9 speed RD I think an Ultegra. Maybe someone else can confirm the capability though.