Audi is coming out with the V12 TDI Q7 that will likely to be over 500HP
Porsche have the 4.5L TwinTurbo V8 Cayenne with 450HP(90K) and 520HP(116K)
MB have the 6.3L V8 ML63 AMG, 500HP with a price tag of 86K
so I wouldnt be surprised if BMW make a V8 or Turbo Charged V8(maybe even a V12?) X5 with around 450-500HP to compete with the other 3 factories, but I would say that they probably want to make it around 80-85K base... since MB and Porsche are both offering 450HP+ performance SUVs starting at 85-90K range.
But the more competitive the market is, the better it is for us, and more choice for us.