The comment from "government" motors made me laugh--they say they will provide what's required without reservations. Since the Feds are major owners of that little enterprise, I couldn't see them saying anything else.
It will be interesting to see what the other major players say and do, especially Ford and Chrysler, given the number of large vehicles they produce.
What happens in the economy may make this whole discussion moot anyway; unless the job situation changes dramatically, many buyers may opt or be forced to continue to drive their old cars way past the time they'd like to dump them. For these regs to may a difference in oil consumption and reduced emissions, you actually have to get the old cars off the road and be replaced with the new ones--not exactly a done deal.