Somehow I doubt that the sulphur regs are going to take effect if diesel is still over $3/gallon. "We can't afford to be good for the environment" they will scream. And the self-reinforcing cycles of oil dependence and climate change continue....
That is mostly a political question.  I've been thinking that if I was Damlier-Chysler I'd be very concerned about this.  The only fuel efficent card in their deck are the efficent European diesels.  So they, at least, should be one member of the oligarchy arguing for low sulphur.  The trucking industry, on the otherhand, is in a lot of pain.  Pain today is a very powerful political motivator.

I don't know if this is a technical question; if the refineries have already made the costly production commitments they may prefer for the regs to go into effect.