Does the 7er get an improved exhaust, or is it purely aesthetic (wheels, shadowline, steering wheel, front/rear fascia, etc.)? That could potentially contribute to the "free" offer.
Also, could they be doing this to increase the number of M Sports available in three years to sell as CPO, which might help move those cars?
I have no idea. Seems less likely to happen on the 6 since it's a pretty popular, big ticket item... But what do I know - I would've bet money that the 2013 wouldn't get the GC's engine, and we all know how that turned out....