Is there any benefit to science from the Swiss built solar plane flying across the globe?
As you can see from the massive delay in its flight schedule, the Solar Impulse II has run into some problems. This is always an indication that something has been learned. Unfortunately, what has been learned is that electric flight is even harder than expected.

The value of this particular airplane is the demonstration that purely electric long-range flights are possible, and in this it ranks with the first rocket-powered airplanes in 1928 and 1929 - yes, it can be done, but for now there is no practical value in it.

As for long term developments - this is just speculation, but I doubt that in 50 or 100 years we will see the Solar Impulse II as the starting point of a new era.