Peace Prize? It could be argued that a better educated world is more likely to move towards peace. Allows people to be more critical thinking and thus not allow themselves to be fooled so easily by politicians.
The Peace Prize has been given for way crazier stuff than what Sal Khan is doing. If a banker can receive it for giving loans to people, why not Sal Khan for educating them?
The Nobel Prize has a famous chilling effect on actual productivity. It's good to give people recognition for their work but I would be wary of giving them too much.