One Nationwide Fuel Economy Standard
The states cannot go off and set their own standards because that will result in a far greater compliance and administrative burden with no clear benefits. Air doesn't stay within state or national borders.
Automotive News and the NY Times (among others) reports that tomorrow the EPA will announce that there will be a single national standard in place for the years 2012-2016. Granted it comes with tough fuel economy standards (basically California's standards - kind of a trojan horse-esque move) but at least everyone will know the rules and be able to get on with the job of actually building cars. Expect a fleet average of 35 mpg in 2016.
The CAFE program is fundamentally flawed (I promise I'll eventually get around to that topic) but this development at least provides some concrete targets for the next several years.