I wonder what that's going to do to the weight of the M5. Even the current E60 M5 isn't exactly what you'd call.......light. As much of a performance car as it is, I wouldn't buy one as a "sports car". I'll take a M5 Touring for the hilarity of it, but for an executive sedan, a 550i suffices. Or a 540i for that matter. If I wanted a sports car, an M3 is good enough for me.