There are a lot of people today who call themselves "Calvinists" who believe that the Church has permanently replaced Israel as the people of God and has taken over all of God's promises to Israel. What I find interesting about all this, as someone who considers himself a Calvinist, is that I reject this theological perspective precisely because I am a Calvinist, that is a consistent Calvinist.
One of the most important aspects of Calvinism is the belief that God is absolutely sovereign in all matters over all time, and that none of His purposes can ever be thwarted. Anything that God sets out to accomplish He will bring to fruition exactly as He plans or His glory is greatly diminished. I firmly believe this.
Some of my friends who believe in limited atonement argue that whatever the biblical evidence that Christ died for everyone (see this post on II Corinthians 5:19), unlimited atonement has to be rejected because that would mean that to some extent Christ's death did not accomplish what it was intended to accomplish. They say that if Christ died for everyone, not just the elect, then God's purpose was not fully accomplished, because everyone is not being saved, and His glory is therefore diminished. I don't accept this application of the principle in question because the scriptures do not say that God's eternal purpose is to save everyone. Christ's death accomplished exactly what God intended it to accomplish, i.e., salvation for the elect and just condemnation for those who willingly reject Christ.
But by this same principle, how can someone who calls themselves a Calvinist say that God called Israel, but they failed God, and therefore God gave up on them and permanently replaced them with the Church. That is not consistent Calvinism. No matter how one tries to present it, this means that the purpose of God also failed to some extent and His glory is also diminished. One cannot have it one way on limited atonement, and then have it a different way on the issue of Israel. Either God is sovereign and His purposes never fail, or in the case of Israel, they did fail. Not surprisingly, the Bible is very clear on this subject.
For I do not want you, brethren, to be uninformed of this mystery, lest you be wise in your own estimation, that a partial hardening has happened to Israel until the fulness of the Gentiles has come in; and thus all Israel will be saved; just as it is written, "The Deliverer will come from Zion, He will remove ungodliness from Jacob. And this is My covenant with them, when I take away their sins." From the standpoint of the gospel they are enemies for your sake, but from the standpoint of God's choice they are beloved for the sake of the fathers; for the gifts and the calling of God are irrevocable. Romans 11:25-29
Notice the last part of this passage, "...the gifts and calling of God are irrevocable". God's Word is saying explicitly that whatever "gifts", i.e. promises to Israel that God makes, have to be fulfilled. Whoever is the object of God's "calling" is going to end up at some point responding to that call. It is impossible for these to be revoked. God's character and integrity are at stake. Israel is in the a time period of "partial hardening" until God has accomplished His purpose with the Gentiles. But ultimately, all of God's purposes are going to be accomplished exactly as He planned. Therefore, as a Calvinist, I believe with the strongest conviction, "all Israel will be saved"!