Pure speculation at this stage, a year from introduction, but how about:

• A sports model with more power, and a much higher price tag
• A model name that is not related to displacement, similar to 335 and 550. Probably (E70) X5 5.0, but not because there are 5 litres displacement.
• No V10 from the M5, since the range would be laughable and the high-revving engine is not suited to this style of vehicle
• A V8 with two turbos, since torque will matter more than hp with this weight. Could be the 4.4 twin turbo that has been leaked in the press, or something larger just to make a brand statement.
• A release date that coincides with the X6 (same powertrain)
• A modified E70 body style, more aggressive.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue