What will God do to the Gentiles who have been grafted in?
God will one day shut the door on the Gentile world, break the Gentiles off from their grafted position, graft Israel back in, and the Gentiles will find themselves again without a Messiah and outside the covenant promises, as Paul says in Romans 11.
Les explains that when God set Israel aside, He brought the whole Gentile world into a place of privilege, not that all are saved, but they have an opportunity for salvation based on the promises made to Abraham. For the last 1900 and some years, Gentiles have been resting and feeding on the fatness of the root of Abraham while Israel has been in dispersion. But the day is coming, and Les thinks it's getting close, when God will once again shut the door on the Gentile world. He'll break them off from that grafted position, and Israel will be brought back in, grafted in again as Paul says in Romans chapter 11. The Gentiles will find themselves again where they were before, without a Messiah and outside the covenant promises.