I think it is important that the ///M division stated they did not want to stick to dogmas. If they stuck to dogmas, there wouldn't be the same level of innovation that we have today. As a result of this, I am almost sick of hearing about "heritage".
Look at the past with the M3. The e30 had an I4. The e36 and e46 both had I6 engines. The e92 has a v8. If they were sticking to dogmas, we would never of had the s65 that we love! Logically the e92 would have an I6.
So this may be a good thing. Right now we are complaining about losing the v8, however the next engine might be better. If we were always scared to innovate with something disruptive, we would never of had the s65 engine that we love today placed in the M3.
Maybe we do not like the sound of a turbo v6 because as the consumer, we do not know what we really want. If BMW always listened to exactly what we had to say, there would be no creative destruction. The consumer would never want the "next big thing" because as the consumer, they do not know what the next big thing is. In order to innovate and create a better ///M car all around, BMW may have to use something like a turbo v6 in an M car, even though some may say it is sacrilegious.