The main idea in vv. 20-28 is that the resolution of all creation is the glory of God in Christ and his resurrection. The last clause of v. 28 makes this clear. The ultimate end of all history is that God may be all in all. The fall and death cannot be the final word. God will win, and he will win in human history. Paul gives three ways God will do this. This sermon covers the last two.
In vv. 23-28, Paul explains how the resurrection of Christ is fundamental to our future hope as Christians and the end of all history. This victory is summed up in v. 28, That God may be all in all. This is where Paul’s argument is headed. The main point of these sermons is that the resolution of all creation is the glory of God in Christ and his resurrection. How is God going to work in creation through the resurrection to resolve all things to his glory?