From what I understand they were wanting to release the 3 series coupe under the designation of 4 series but that would mean an M4 instead of an M3 so its a no go.
The 4 coupe should be debuted in 2013, with a launch date in 2014, the convertible a year later. It is rumoured that the odd and even designation for saloon/hatch and coupe respectively will be continued accros the range
