Just a note... You can have a vehicle dyno tuned for a specific gas type, and it will take the ethanol content into account, and offset the economy loss. It surprises me that cars don't have specific fuel maps for ethanol gasoline, seeing as pure gas is very rare.
With everything else they are doing to meet CAFE standards, simply changing the timing/ignition and fuel maps is practically free and good for economy and for power, with no downsides.