The internal combustion engine has pretty much reached its ultimate efficiency/power/torque limits. There aren't any more tricks in the bag to improve them. The Auto Companies are going to meet the 40mpg standard with battery/electric propulsion. Let's hope they start putting charging stations that will ACTUALLY have capacity to meet demand on the Rubicon.
FWIW, I had sales contract ready to sign for a new Wrangler 4xe hybrid till I actually compared its cost to operate with the electricity costs in Kona. It worked out to nearly 6$ an equivalent gallon to charge the battery in the 4xe compared to the then $3.50 a gallon to run the Jeep on just on gasoline. If fossil fuel costs continue at this level your electricity costs are going to rival those in Kona and an electric or hybrid is going to cost just as much or more to operate than a similar ICE powered car.