Doubt that the character line at the top of the grill will make the M5.
The F10 bumper extends all the way up to the grill and that character line. If they keep the mold that makes the M5 front bumper, I have a hard time believing they'll remold the M5 bumper to include a slight character line at the top.
Then we're talking lights, which is not a big deal.
The E39 2000 -> 2001 shift was huge, though, so hopefully not along those lines (tail lights, angel eyes, 16:9 nav, less dorky steering wheel).