If BMW took the time to design an I6 along the lines of the old RB26DETT motor for the new M3 I think most people will be quite happy indeed... Tons of power, 9000rpm redline and all that was from just 2.6L
If on the other hand they are planning to just upgrade the N54/55 motors and call it a 'high-revving' engine then I will lose all respect for the M brand!