I am OK with 4 cylinder turbo in M2 as long as the M2 is a lot lighter and under 3000 lbs in weight. If the 4 cylinder makes close to 330 plus horsepower and torque in such a light weight package it will be a beast of a car from performance point of view.
Also, more then the engine cylinder count I would like to see a very free/fast and fairly high revving performance engine that sounds great. It offers great fuel economy and does not have narrow band of power.
My biggest concern with future M cars is not with the engine choices but rather the electric steering wheels. These new electric style steering wheels rob the great feel and feed back we have all come to expect from current hydraulic setups in BMW cars. All I know is I have not been impressed with the steering feel of the back then all new 2011 F10 5 series with or without the sport plus settings. Too artificial for my taste. I was glad to get back into my E92.
nick named "BAD 3"
Cobb tune, RennArt catback non resonated exhaust, M-sport steering (racing alcantara & retrofit M3 paddle shifters.), Alpina B3 transmission flash, AFE powered sealed CAI, LED angels, E93 M3 Front Swaybar, 235/35/19x9 front & 275/30/19x9.5 rear. When in doubt...flat out