The concept of the lost tribes of Israel is a misnomer. They may be lost to men, but they have never been lost to God. The Scripture clearly anticipates the regathering of the whole house of Israel from all the tribes. The book of Revelation even declares that in the time of Daniel’s70th week (the Tribulation), 12,000 will come to Christ and be sealed from each of the twelve tribes of Israel (see Rev. 7). But that’s not all, the Old Testament emphatically declares that God will gather Israel, after being scattered all over the earth by the dispersions, from even the four corners of the earth (see Jer. 23:3; Isa. 11:11-12, 16; Jer. 31:7-8; 32:37). Furthermore, Romans 11 speaks of God’s future work for the nation of Israel. Much of the following comes from The Ryrie Study Bible and will help answer this question.
At the moment, there is a partial hardening in the nation of Israel. This hardening is partial (Jews are being saved today) and temporary, until the fullness of the Gentiles (i.e., the full number of Gentiles who will be saved) Acts 15:14). After that, God will turn again to the Jews and will save “all Israel” at the Lord’s return (v. 26).
When Israel rejected their Messiah, Jesus Christ, the nation lost her favored position before God, and the gospel was then preached also to Gentiles (Rom. 11:15). Hopefully the Jews would become jealous and be saved (v. 11). But the casting off is only temporary. When the Lord returns, the Jewish people will be regathered, judged, restored to favor, and redeemed (v. 26). This will be for them life from the dead.
The olive tree is the place of privilege that was first occupied by the natural branches (the Jews). The wild branches are Gentiles who, because of the unbelief of Israel, now occupy the place of privilege. The root of the tree is the Abrahamic covenant, that promised blessing to both Jew and Gentile through Christ (Rom. 11:17-24).
In Ezekiel 37 there is the prophecy of the future regathering of Israel to her land even though it will start in unbelief. Ezekiel predicts the political and spiritual revival of his nation (vv. 1-14) and the reuniting of its two divisions (vv. 15-28). The dry bones indicate an army slain in battle, a fitting description of the then hopeless condition of Israel. Verse 9 says they will come from the four winds (i.e., from the four quarters of the globe).
Of course, claiming that God has rejected his people and abrogated his promises to Israel, many today try to spiritualize these passages and apply them in some way to the church, but a literal (natural) and normal way of interpretation recognizes that, though God has set Israel aside for today, he has plans for them in the future (Rom. 11) and that these verses will be fulfilled in the future. Since 1948, we have been seeing the ‘clinking of the dry bones’ with Israel returning to their homeland, though in unbelief. In the future, God will bring them to faith through the judgments of the Tribulation as described in Revelation. Note that Ezekiel 20:33 anticipates a future regathering and judgment of Israel: