Wow, people are really emotional on these boards. These are Germans. They are logical. Based on the naming of the rest of the series, the F30 Coupe/Convertible should be the 4 Series, including M4.
Don't worry, the M3 may live on, as a sedan!
This is long overdue in my opinion. Should we name the 6 Series the 5 Series Coupe instead? If you are going to use alphanumerics nomenclature, make them so that they actually follow a formula. It is bad enough the last two numbers are now nominal displacement and they do not designate body style or drive train type any longer with letters.
I'm sure everyone will welcome the 2 Series since the next 1 Series will be FWD.
Rename the 1 Series M Coupe the M1 while you are at it. Who cares about a sub-par 70s supercar. I don't, because my Sedan will eat it for lunch.