I think thats a bad move unless they keep the engine very small and light. The ideal thing about the M3 is weight distribution, if you look in my dads E46 you can only see half the engine, the rest is under the dashboard, so the engines not on top of the front axle like in Audis etc, ill be very impressed if they can get a big V8 under there unless the car is bigger (and the M3 is already too heavy) or they make a completely new engine.