2015 BMW M4 Concept Coupe
Based on what we've seen in previous BMW M "concepts", this is probably 99% representative of the final production model. Full reveal is this weekend.
Rumor is a tri-turbo I-6: 415hp, 400lb-ft of torque. Probably going to be about 300 lbs less than the outgoing E9x series, meaning it could clock in at 3400lbs (yet packing an extra 100lb-ft of torque)!
This "tri-turbo" setup is likely to be the standard twin-turbo (like the new M5 & M6) with an electric turbo assist.
The exhaust/engine sounds I've heard so far are a disappointment, though. It will probably have the ridiculous "engine sound through the stereo" thing, i.e. $1500 in electronics to cancel out 500 lbs of sound deadening. The turbos muffle everything and the amazing rumble of the V8 is of course gone...that seems to be slowly driving the prices UP on the used E9x M3.