I think there is just more rock on the far side of the moon. There is no part of the moon which has not been seen by us on earth. The astronauts and space rovers that we have sent to the moon have never returned with anything except rock and we have no reason to believe there is anything else there.
It is possible there are things that were discovered on the moon that governments are not telling the public, but that would just be wild speculation. I think it is more likely that we will discover something interesting on another planet rather than the moon, which is just a rock.