Had a chat with my buddy at BMW in Munich recently and he told me that all M cars will have a viscous diff/clutch AWD system sooner or later.
He works in R&D but I've told you that already:
And now before the people start crying "Oh BMW have lost their way. First cars with even numbers, then cars with even numbers and an X..." and so on, let me tell you that it will be RWD biased. The idea is that you can put the car into a drift using RWD power and when they loose traction the front wheels also get power so that you can put the steering wheel straight and keep that drift angle forever and ever. Or that's how I understood it.
And don't despair! There'll even be a RWD-only mode. Selecting that will also disable traction control for some good old fashioned hoonage. To fully disengage the front wheels they plan on letting the oil out of the viscous thingy and pump it into a reserviour or something (again not an engineer, I only understood half of the technical stuff).
While I like my M cars manual, naturally aspirated and RWD, I think I can live with this. But I'm sure the internet is full of haters, so let the bitching begin and get it over with rather sooner than later.