The Teaching of Jesus — p. 105
It would be an odd thing for Jesus to teach His disciples to pray this prayer if there was never any intent for God’s Kingdom to come except for a sudden eschatological inbreaking. No, the premise behind the prayer is that the Kingdom that is being prayed to come will indeed come to fruition in space and time over the course of the years of human history.
The OT saw the Kingdom of God coming immediately and eschatologically, as if once it came that was all there was. When Jesus arrives bringing the Kingdom He communicates via His healings, casting out of demons, and exercising power over the natural realm, that there is an immediacy to the Kingdom — the Kingdom has come. However, Jesus also communicates that the Kingdom while coming in His person and ministry, also has an eschatological future that will find the present Kingdom that has come in Christ to be even more of the same. In the ministry of Christ, the seedling of the Kingdom has been planted and that seedling is expressive of the power of the Word. However, the seedling grows and grows, renewing and reforming and bringing life to wherever it roots so that in the end the Kingdom of God covers the earth as the waters cover the sea.
Another way of expressing this is that Jesus Himself in His coming brought with Him the long-anticipated age to come. That age to come has been given an outpost here with the life, ministry, and death of Christ. The purpose of the presently planted age to come though is to roll back the opposition that is this present wicked age. So, the Kingdom of God is where the age to come is located and that Kingdom of God is defeating the enemy and their luciferin Kingdoms in this present evil age.