There are many who expect a worldwide conversion of Jews before Christ can again return in judgment, and for the most part that view is based on this verse. I thought that Calvin's words on this verse would provide some food for thought, as well as a confidence in God's preservation and salvation of his Church - who have been ingrafted into Israel.
Many understand this of the Jewish people, as though Paul had said, that religion would again be restored among them as before: but I extend the word Israel to all the people of God, according to this meaning, — “When the Gentiles shall come in, the Jews also shall return from their defection to the obedience of faith; and thus shall be completed the salvation of the whole Israel of God, which must be gathered from both; and yet in such a way that the Jews shall obtain the first place, being as it were the first-born in God’s family.” This interpretation seems to me the most suitable, because Paul intended here to set forth the completion of the kingdom of Christ, which is by no means to be confined to the Jews, but is to include the whole world. The same manner of speaking we find in Galatians 6:16. The Israel of God is what he calls the Church, gathered alike from Jews and Gentiles; and he sets the people, thus collected from their dispersion, in opposition to the carnal children of Abraham, who had departed from his faith.If Calvin's interpretation of this verse is correct, then Romans 11 is concerned - not with spelling out the fate of ethnic Israel, but with reassuring the church that the hardening of Israel took place so that the true Israel could all be saved.