You guys are making it more complicated than it is...
From all the hints they have been giving us, here's what i can gather...
Previously, the 3 series model is made up of : Sedans, Coupe, Convertible, and Touring
Now, it would seem that BMW's small sedan model is broken up into two series:
3 series for the 4-door models: sedans and tourings
4 series for the 2-door models: coupes and hardtop convertibles. (2013)
Therefore the corresponding M# series for those models will be:
M3 = sedan (2013)
M4 = coupe/convertible (2015?)
So now we will have "2" choice of "M3": the M3 which is now a sedan, and the M4 which will be a 2-door monster...
any more questions?