Originally Posted by XFiringInNC
Presumably, if you were downshifting and not also hitting the brake, you weren't trying to slow down drastically as much as perhaps you just selected the wrong gear. Whereas, if you really WERE trying to slow down drastically, you probably hit the brake, thereby disengaging the cruise control anyway. No extra steps necessary.
But I don't know any reason to downshift unless one is about to change speed.