This would mean that BMW would probly put a V12 into the next M5/M6. BMW has to be aware of the tuning potential of factory turbo motors, considering what's happend with the 335i.
I spose it's a similar situation that they are in now, with the 335i and M3. Although I would think that for the next gen M cars they are going to want to seperate them a little further. BMW has to know that the 335i is going to hurt M3 sales a little bit, I dont think they are going to do this again. This is all IMO of course, but once you start offering TTV8's it's hard to get hyped over an NA V10.