EV Affordability or Gas Engine Efficency? Determining America's Transportation Future

Which will come first: Vehicles like the Chevy Volt becoming more affordable (unsubsidized) or gasoline, and diesel, powered cars achieving the fuel efficiency of vehicles like the Volt (60 mpg)? Whichever reaches their ultimate goal will determine America's automobile future. If I can buy a Volt for $20,000 or a regular gas/diesel car that gets 60 mpg for $20,000, I am going to do that. Whichever comes first is going to be the game changer.