I'd like to see us get the new 3.0 liter diesel debuting in the new F01 7 series here. I believe it is the more fuel efficient, single turbo version but is now making 245hp instead of 225hp. I think this would be more ideal for the 3-series, would be cheaper to buy up front, and would show better fuel economy than the 335d. i'd imagine this 245hp version of the engine will be in the new 330d following the face lift.
ideally however, I wish that the 323d would make it here to North America. 2.0 liter, 4-cylinder, twin-turbo diesel with 204hp and 300 ft-lbs of torque. And very frugal. This would be the engine for me!