Solar power satellites are getting more feasible all the time.
Unlike some space enthusiasts, I think it will be easier to come up with a lower-cost launch system to launch components from Earth than to develop a lunar industry that manufactures them and kicks them into Earth orbit (although given the premise of an existing lunar industrial system - a pretty big premise - that would be the cheapest way to go).
The industry needs a "killer app," the equivalent of a gold strike out there.