Why is the Gentiles' day coming to a close?

Les explains that Israel was set aside for over 1900 years, without temple, priesthood, sacrifice, and without a homeland until our generation, but God is not through with His covenant people. In the grafting process, Israel was removed and Gentiles were placed over the root of father Abraham. Gentiles have enjoyed the blessing of having the gospel and the opportunity for salvation, but their day is fast coming to a close because they too have been walking it underfoot. God's grace and patience will one day soon run out, and He will go back and pick up where He left off with Israel. Paul writes to believers in Romans 11:25, and in the age of grace those are predominantly Gentiles, though some Jewish believers also exist. He warns them not to be ignorant, noting that ignorance is not a lack of intelligence but a lack of having been taught something.