They have it easier than most, given they have cars that are rated at 70mpg+ in their lineup. But it's not enough to just sit on that, in the years to come, the figures they have to meet are going to be outrageous.
Look at the small time guys like Aston Martin.
They were never going to meet the future goals, so they bought some of these:
http://i.imgur.com/fXFZP.jpg
Put some leather, badging, and hood scoops.
VOILA:
Aston Martin Cygnet:
http://i.imgur.com/AlLC1.jpg
The D4 S8 is far faster than the old 5.0L V10 S8, and does everything better including a HUGE jump in fuel economy.
I really don't see any issue with the technology. Especially as, even for a million dollars, you wouldn't' be able to point out when it switches from 4->8 and vice versa.