IIRC, that car will no longer be called M3, but M4. BMW plans to build 2-doors that no longer look too similar to their 4-door siblings, hence the 4-Series. However, there's speculation of the M3 sedan and wagon, something not offered during the E46 heyday.

A V8 producing 400 hp is said to be the new engine. They claim that such output is hard to attain from the legendary straight-6 design. I do wish though that there will be a high-powered 6-cylinder 3/4-Series that bridges the gap between the 3-liter and the M.