If you compare the e90 vs the f30, the f30 is supposed to be 88lbs lighter, but actual numbers don't show that much weight loss.
Searching the forums, you can find 6mt e90 335s on a scale weighing very close to 3700lbs. With the M3 weighing more than the 335, I wouldn't be surprised to see the larger F80 M3 with DCT and all the creature comforts to have similar weight as the current model.
Like everyone else, I want lighter, but would be content with no weight gain.
oh and diavel