I know just how you feel. I too wanted the new iDrive and had all the info regarding its introduction in September build cars. Mine had an October build date, so I was quietly confident that I would get it and I did and let me tell you it's fantastic. You will love it.
I assume you perhaps got Nav Pro and Logic 7 Pro as well.
Your only issue now is that you are probably relating your delivery time to the day (or near to) the ship arrives at Port Kembla. Let me tell you on average, you still have a relatively long frustrating wait.
Mine took 11 days to clear customs and arrive at BMW's holding yards. Then there was a couple of days to go from the holding yards to BMW wholesale at which time they organise transport etc etc etc. Bottom line.. ship arrived at Port Kembla on the 1st December, finally got the car on the 16th December.
At the end though, I expect you will be like me with a grin from ear to ear everytime I get in and drive the car.