It will gain some weight on its way into the US, and the EPA has its own test for MPG. I'll be surprised if the highway mileage is below 30. Hell, I'll be surprised if it's below 35. Lightweight, good aero, and direct injection should make it very efficient.
As it is right now, I can average just about 29mpg on the highway in my spec.B and that's a 3500lb turbocharged car with port injection.