From what Ive heard the new M5 and m6 will have 580hp with the same motor thats in the X5m. they are only gonna tweek software and cooling.
The car will have a 7k redline and over 500lbs of torque available right above idle pretty much. Peak hp will come in in the high 5k rpms and run flat up until just before redline. The M5 will not use the auto box in the x5m but it will use a MDCT tranny that is seriously beefed up for the M5 motor. The new car will be around 4000lbs again just like the V10 m5 its replacing.