Although the prototype design appears unconventional based on the way we currently envision commercial aircraft, MIT is serious: the technology exists to substantially decrease fuel consumption while not compensating performance. Take a look at their proposal, at left, for the future of Boeing’s 737 program.
The new design would have a "double-bubble" shape instead of a single-fuselage cylinder, which would make possible a smaller tail (thus reducing drag) and longer/skinnier wings. Rather than placing the engines on the wings, a "boundary layer ingestion" technique would be employed, allowing the engines to sit at the top rear of the fuselage and draw in slower-moving air that passes over the aircraft. The result: less fuel for the same amount of thrust.
The plane would have to travel about 10% slower than current 737’s travel, but developers contend that the dual-aisle cabin would lead to faster loading and unloading.
What is missing from the article is an analysis of cost. This sounds like a great design, but if raw materials, engineering, and testing costs are too high, it is not even worth discussing further right now.
It is fun to speculate, though. Take a look at the link above for other futuristic aircraft designs, including an update on the 777 and supersonic designs from both Boeing and Lockheed that could be in production in less than 20 years.