A long, long, long time from now, when we have some sort of very advanced propulsion system that uses barely any fuel, but also is decently fast enough with a large load. It will also need to be for something used in orbit as getting large amounts to earth would be very difficult.
It isn’t as hard as @XOIIO speculates, since getting into space from the moon doesn’t require the propulsion that it does from Earth.
The movie Moon isn’t far off how it will be done.