I expect it will in time...

This is an excerpt from the recent Motor Trend first drive of the 2011.

"Then there's the BMW xDrive40d, which the automaker brought along to showcase its updated diesel technology. Though not offered in the U.S. (at least not for 2011), the xDrive40d is powered by a retuned version of the xDrive35d's 3.0-liter twin-turbo I-6 that packs 306 horsepower and 442 pound-feet of torque and is fitted with the same eight-speed transmission as the gasoline models. With the xDrive35d accounting for one-third of X5 sales, don't be surprised to see the new diesel in America relatively soon."

2011 BMW X5 xDrive35i Specs - Motor Trend


I'd be surprised if BMW brought along a 40d for the U.S. launch meeting for U.S. magazines if they weren't seriously considering bringing it to the U.S. at some point in the not distant future, perhaps 2012.

But that's just my opinion.