I have read this weekend in the French Sport-Auto: the reason why Subaru will not sell the WRX in Europe shortly is because it would push the average fuel consumption (and consequently the CO2 emissions) of Subaru to a level that would cause penalties for them.
So, for the moment they will sell only the STI (which, since it will sell few cars, won't effect the average so much) and the WRX will only be sold after the Diesel has lowered the average.