I doubt that BMW will introduce the 20d engine in US. Especially with low fuel prices. I think that it will be either 30d or 35d. As first diesel F10 in US they will try to offer more performance so they can convince drivers to save money and the planet keeping the performance high. The interesting part is that 30d has a performance very close to 535i. So if they offer 30d at same price like 535i I guarantee a lot of people that are already convinced to the new F10 will take advantage. Especially since the diesel version will give you more than 30% better economy. Here is a
F10 catalog (page 29) with the EU Fuel consumption data where you can see the difference between 530d and 535i.