This is similar to the Dilema which applies to X5 aswell - No M-Powered X5 (although the US wants one, To which BMW have already told them No!) But M-powered X6 .

With the M-series the M5 has a more passionate ring to it than M7 , many within BMW feel that M7 would be a "follow Audi , MB" project . So it is possible that the top line M car would be upcoming BMW's Gran Turismo four door Coupe which would deserve and illustrate the M-status better than the
7er.
Leaving the V8 Turbo 7er to be the sole performance model within the range.