A few quick thoughts…
- Arguably in Romans 9-11 for Paul a remnant of believing Jews constitutes the true Israel.
- The phrase “Israel of God” is difficult (Gal. 6:16), but it’s certainly an option to maintain that Paul thought of the churches as restored Israel, now combining Jews and Gentiles under the sort of new covenant prophesied for Israel in the Old Testament.
- Gentiles are included in the “commonwealth of Israel”, which keeps “Israel” foundational for the identity of the movement (Eph. 2:12).
- The writer to the Hebrews highlights the fact that the new covenant would be made “with the house of Israel” (Heb. 8:8-12).
- The new Jerusalem is said to have a “great, high wall, with twelve gates, and at the gates twelve angels, and on the gates the names of the twelve tribes of the sons of Israel were inscribed” (Rev. 21:12).
I don’t think Jesus foresaw the inclusion of large numbers of Gentiles in new covenant Israel, but it seems to me reasonable to say that his vision of restored Israel essentially runs through the whole New Testament. With time, of course, the defeat of Israel by Rome in the period AD 66-135, the breakdown of relations between Christians and Jews in the 80s and 90s, the shift of the centre of gravity to the Greek-Roman world, and the overwhelming preponderance of Gentile believers put an end to the vision of Israel restored. But I think that largely belongs to the post-NT period.