Decades after The Jetsons forecast flying cars and 2001: A Space Odyssey promised interplanetary travel for the everyman, we've awoken to the sobering lesson that radical change takes time.

That said, today's auto industry is morphing quickly, and some predict that within two years, the U.S. car market will have undergone a dramatic shift. 

According to Gas 2, those predictions come via Navigant Research, which has analyzed recent sales trends to issue forecasts for the coming decade:

This Navigant Research report analyzes the emerging global market for technologies that improve fuel economy. The study examines the consumer demand and regulatory background related to features and lightweight materials for increasing fuel efficiency in vehicles. Global market forecasts for [light duty vehicle] sales, segmented by powertrain, region, and number of cylinders, extend through 2025. Additional forecasts by region are provided for the volumes and associated revenue of key fuel efficient systems and materials. The report also examines the approach of the leading vehicle manufacturers, suppliers, and industry players and evaluates how the market for lighter and more efficient vehicle technologies will evolve.

Among Navigant's most intriguing predictions is that by 2017 -- just two years from now -- fewer than half of all U.S. automobiles will make use of simple, conventional gasoline engines.