Could it be that Intel is keeping DDR2-667 support for yet another revision of their new chipsets even though the memory support is clearly here today?

sure why not? intel could be postponing on brining out their biggest guns for later on when it would be better to shoot them off, they might also want to see what the competition will do and bring out before they bring out their best, but on the same note, who knows what else Intel might be holding back? They might have some other amazing thing that they are waiting to spring on the public at an appropriate time...