In this passage, Paul goes much further. It is not just that biological descent does not necessarily make one a member of the people of Israel. God can reject the biological heirs and replace them with persons who have no biological descent from Abraham. The Gentiles who have faith in Jesus Christ have been "chosen" by God to replace the Jews who have rejected faith in Jesus Christ.
In Christian literature, Christians (whether of Gentile or Jewish origin) will be known as the "True Israel" or the "New Israel"; the Jews become "Israel of the Flesh," the "Old Israel." This will eventually allow for a new spin on the verse, "The older will serve the younger," as we will see.