Prius drops to 48mpg; How will 2008 Prius get 80mpg? Plug-in hybrid?

The National Center for Policy Analysis reports: CAR M.P.G. RATINGS GOING DOWN. The cars aren't actually getting worse mileage, but the government's new tests going into effect next year more accurately reflect real-world driving.

Fuel-saving gasoline-electric hybrid cars don't save as much fuel as thought, according to new government fuel-economy ratings available to the public for the first time.

The new ratings go into effect beginning with 2008 models, a few of which will soon be on sale. But now it's possible to tell what rating 2007 and older models would get using the 2008 standards.

Toyota's Prius, the best-known and best-selling gas-electric car in the United States, drops from a 60 mpg rating under the current system to 48 miles per gallon in the city under the 2008 testing procedure -- a 20 percent decline

Its highway mileage rating falls about 12 percent, to 45 mpg.

The Ford Escape hybrid, which uses a gasoline-electric drive system similar to Toyota's, goes down about 12 percent.

So how will the 08 Prius, rumored to get upward of 80 mpg achieve it? Can it be done without making the high-mileage leader a plug-in hybrid?