I really don't think it matters what they call it....Audi has the A4 sedan and the A5 Coupe, this makes sense.
Also, the new naming convention of cars has to start sometime, so why not now? Unless BMW moves away from the numerical series names.
Acura made some major changes years ago, with the Vigor being refreshed into the TL and also the move away from having any proper names and just a series of 3 digits.
'11 BMW Z4 35iS
'12 Mini JCW