My understanding is that the MPG is supposed to be acrossa vehicle type for a company. For example light trucks are a vehicle class so whatever is in that class as a whole woul dhave to average 35.5mpg not every vehicle but on the other hand no longer can they make a slew of small economy cars to make up for the gas hog trucks and SUV's.
So what we are going to start seeing IMO is that vehicles will start getting smaller and they will start losing weight via lighter materials as the easiest way to increase MPG. Ford already has plans to start losing weight on their vehicles.
along with all that, what about putting in a higher rearend gear or a 50% overdrive. if they're producing the power make the gears taller, the first thing most people do is a gear swap anyways.