Difficult to answer your question not knowing which country you write from. Mind you even if I knew I wouldn't know your Business Practices Code anyway !
Okay seriously now... As mentioned up here, it boils down to good customer service. If a brand new car is not in by the delivery date written on the order form, the least a dealer can do (especially a BMW dealer) is provide you with a courtesy car until yours is ready. Speak to him.
BMW is judged on the cars they make, dealers on the service they provide especially when there is a glitch.
Happened to my wife in 2008 on her first Mini Clubman, delivered 2 weeks behind due date. Never had to ask, the sales rep at BMW informed her she'd get a demo Clubman until hers got delivered. I'd say that's service.