Inline 6 diesels are already here in the 730Ld and the X5 3.0d, the only reason it isn't in the smaller and cheaper cars like the 3 is because the engine size is over 2000cc so the price would shoot up due to tax going up. The only diesels that can't be brought here due to fuel quality is the twinturbo models in the 740d, 535d, 335d etc.