In March of this year BMW changed the entire steering rack/motor/control assembly and the part number is the same as that fitted to the F12 640i.
I've driven the new 6 series over a period of several days, totalling about 600 miles over all types of road surfaces and conditions. The steering is far more responsive, but that could be due to different programming, wheel size (20") and tyres. However, the vague on-centre lack of feedback is still present, albeit to a far lesser degree.
Like many other posters, I think this is due to BMW switching from hydraulic to electric assist steering and it looks like we're stuck with it. The new F10 M5 also has electric with M Servotronic; don't know whether the 'M' will make any difference, but if it doesn't, I think BMW will be losing a lot of M car loyalists.