CAFE applies to the average of all cars SOLD by the company, as I understand it.
The idea is that it allows for niche performance cars to exist, but they must be made up for by higher sales of more fuel efficient cars (legislating for taste?
)
The long term net effect is that V8 cars will likely grow more expensive to reduce their market share, with turbo 6's taking over the role.
I'm betting that by 2015 the mustang GT will be a turbo 6, with the 8 cylinder slotting in as a 35k+ cobra or boss model. Hell, there's some talk that it could be in 2011 with the new coyote engine.
I imagine something similar would happen with the camaro.