Did you get one already???
Is that with 6MT or DCT? That's a little bit heavier than I expected. My 6MT e92 with half tank weighed in at 3550.
BMW USA specs page has curb weight for auto at 3595 and 6MT at 3540. The coupe is very slightly lighter. http://www.bmwusa.com/Standard/Content/Vehicles/2015/M/M3Sedan/Features_and_Specs/M3SedanSpecifications.aspx
that's with a 6 sped, steel brakes, CF roof, and a bunch of other options like HUD, Premium stereo, big wheels...
for a brief moment
Details coming soon I hope??