God’s reign is total, complete and absolute, revealed in the resurrection of Jesus Christ. So the mission of God’s people is not to extend the reign of God, as if God’s reign needs extending. God’s reign is perfect and complete – it does not need extending.
So then the mission of God’s people is not to extend the reign of God. What we can do on mission is to clean the windows of the lives of those who have not yet been set free, so that they too can see the magnificence and creativity of the Triune God who reigns supreme. We are window-washers in the Kingdom of God.
The mission of God’s people is not to extend the reign of God. God’s reign is complete.