“Yet the time will come when the Lord will gather them (the Jewish nation) together like handpicked grain. One by one he will gather them—from the Euphrates River in the east to the Brook of Egypt in the west. In that day the great trumpet will sound. Many who were dying in exile in Assyria and Egypt will return to Jerusalem to worship the Lord on his holy mountain” (Isaiah 27:12-13).
I believe when the trumpet is blown and Jesus takes His church, the remaining, unbelieving Jews scattered in the world will be returned to Israel by God. There will be a great revival among them (led by the two witnesses of Rev 11), and all of Israel will be saved during the Tribulation.
“Some of the people of Israel have hard hearts, but this will last only until the full number of Gentiles comes to Christ. And so all Israel will be saved” (Romans 11:25b-26a).