Well, the BMW weight figures posted are dry weight not curb weight. That means BMW's figure for the weight of the car is with no fluids or fuel. Obviously the car can not be driven like that so when the vehicles actually are driven off the lot they will be over 3400 pounds. BMW did this on purpose to skew the weight figure for attention and to exaggerate their weight loss figures.
BMW confirmed the weight for the M4 is the dry weight in the press release for the new 2014 M4 DTM car, "The BMW M4 Coupé itself is a prime example of intelligent, lightweight construction. The high-performance sports car weighs just 1,497 kilograms when empty – that is a whole 80 kilograms less than its predecessor."
So, expect E46 M3 levels of weight for the car and not the 3300 pound range we were misled into believing. Yes, still lighter than the E9X. Just not by ~300 pounds.