This effort is continuing as DARPA’s Vulture II, but the program has been re-scoped and as a result of that, Boeing is not building a demonstrator, aka SolarEagle.
These artist’s concepts are no longer applicable to the program as of January 1, 2013.

SolarEagle, a 400 foot aircraft powered by solar energy, will carry a ‘pseudo-satellite' payload of up to 1,000 pounds in the high stratosphere (above 60,000 feet). Designed to stay aloft for five years and generate a five-kilowatt power supply, this re-positionable platform could provide unprecedented persistence in ISR and communications missions.