Making the M3 a v8 sounds good on paper, but any owner of the current e46 M3 will tell you that the 333HP, high revving V6 has PLENTY of power.
If you drive it without any aides like traction controll, or spin control, the car is hard to keep from spinning out at first. Trying to power slide in this car takes real skill and control, and is scarier than all hell! The torque and low end power of this car is serious. Unless the new M3 is much heavier, I can't see why they made it a V8, unless they just want to be on par with the Audis and Mercs that compare.
Then you consider the issues the new 3 series is having (like most new cars have), I would like to wait until they work the kinks out to get this one.
I'll be looking for these on the road next year....