"this gospel of the Kingdom must be preached to all nations, then the end will come." "The whole earth will be filled with the knowledge of the glory of the Lord" "I will pour my Spirit out on all nations" "Every knee should bow and every tongue confess..." Many of these verses have been taught with an emphasis that it is something yet to come.
Are these references to end time scenarios?
Or does the New Covenant understanding of what God did through Jesus Christ show us something that makes us appreciate the finished work of Christ even more?
I think the latter, and I think this key will open up scripture both in the Old and New Testament in a whole new way, and you will see how amazing of a place you are in right now because of God's foresight and plans to have you join His family!