Like said before many times:
M brand (just like BMW brand) has certain values & philosophy that can be achieved / delivered via different technology. These values & philosophies are not tech-dependent.
Eg. when BMW engineers will be able to develop & produce a certain tech (at right price!) that will fit the brand perfectly, then such tech will be introduced & offered.
It is stupid to assume certain tech is associated with certain product / brand. Tech changes. Tech development is constant. Sticking with "old" tech (especially when competitors are using better new one) is a formula for a disaster.
Turbos in M? DiesOtto engines in M? SuperHybrid M? All that is possible.
Mind that eg. F1 is going green, and all such super-performance + green tech will be developed & at certain time point also offered in production cars. So, if a turbo engine, DiesOtto engine, or a SuperHybrid will be good enough to be used in F1 cars (incl BMW ones) I'm sure such tech will be more than perfect to be featured in BMW M models as well.
So, currently high-rev NA engines fit M brand best. But that can change in the (not-so-distant) future when alternative tech is available - an alternative tech that will be able to express & deliver all the M values, promises, experiences.
