Arguably, this is what has happened with Maul on The Clone Wars.
I think part of the problem is neither follow up villain was as compelling as Maul. The mystery about Dooku's true allegiance didn't last very long.
One of the animatics for ROTS make Grievous appear to be Maul reborn as a cyborg, but I've no idea if that was a idea Lucas was considering or the animators having fun with it.