Idiotic...no.
Would I...no.
More then likely all tour accessories will fir the 9650 but with the slight shift of the keyboard and unknown battery door I wouldn't risk it. We saw pictures of new charging cradles that both the Tour and when it was still called the Tour2 both fit into.
So if having a case for your phone right away is important for you I would say you are safe in buying it but I don't really need a case so Im going to hold off on buying anything...until it is at least announced.