Nope. I know Chrysler will produce their concept cars: the Dodge Viper R/T is a classic example. So is the Dodge Dart, the Dodge Stealth, and the Dodge Challenger...just to name a few. The same holds for GM and Ford. Even Mercedes and Porsche will turn one of their concept cars into production vehicles (e.g., Porsche 911 Concept back in 1985 which turned into the Porsche 959).
What BMW's excuse is this: we take CERTAIN ASPECTS from concept cars that we think will make our current lineup better, and adopt those aspects (e.g., suspension, braking, etc.) into the current vehicle designs.
Translation: We're too scared to try and actually put out a completely NEW concept turned production vehicle...because we are afraid it'll cost far too much and it won't sell very well. So, we're scared, but instead of saying that, we'd rather just put up some garbage stock set of answers that we have. to keep you confused. :D