BMW currently offers their X5 SAV with two engines, a 3.0 liter straight 6-cylinder making 272 hp and a 4.8 liter V8 making 355 hp. But these latest photos indicate that a new, even higher-performance X5 is on the way which is likely to be called an M model, in accordance with the usual BMW nomenclature of its high performance models. Engine is unconfirmed, but the next logical choice would be the big 6.0 liter V12 from the 760i sedan which produces 438 horsepower.
One indicator that this X5 has a more powerful engine can be seen in the huge exhaust pipe tips. They are noticeably larger in diameter than the exhausts on the 4.8 liter X5. Plus the front bumper is completely redesigned with larger air intake openings to allow better airflow to an extra-large radiator. The front bumper also appears to extend lower, making it more of an air dam, helping to prevent turbulent air from going under the vehicle, thus reducing drag, especially at high speeds.
The X5 is no stranger to a V12 power plant though. Back in 2000 BMW showed the X5 Le Mans experimental vehicle which had the legendary German racer, Hans Stuck, whip this 750 hp (514 kW) monster around Nurburgring in 7min 49.92sec. Video of Hans Stuck driving X5 Le Mans
Assuming it does get the V12 (and that's a big assumption), it would be the X5 6.0is. I'll take bets on that.