I agree with most here. I do think the M5 changes give some insight about the percentage improvements. However, I also think, as Mapezzul pointed out, the M3 is the drivers car of the M division. It is their "meat and potatoes" car, and will be more likely to undergo significant technological advancements (compared especially to the M5 changes). I would bet we will see an F80 M3/4 with sub 3500lb weights and >/=450hp. Also, the tri turbo inline 6 making 450ft/lbs at <1500rpm. 0-60 runs in 3.5-3.8 sec range and maybe even fuel economy in the 17-25 range (please).
Overall, will be a winner and continue to set the benchmark!