With oil prices over $65 per barrel, every increase in mpg can result in big savings.
I think we'll start seeing fleet vehicles using alternative fuels and engines. I read somewhere that UPS had ordered a bunch of hybid engine delivery trucks.
Fuel is not the biggest expense in owning a car, just the most prominent. Also the lighter a car the more life threatening the injuries can be in a crash. At some point higher mpg results in higher total cost.