Did Isaiah connect Israel's blindness to the time when God would turn to the Gentiles?
No. Isaiah did say Israel's table would become a snare and that they would be blind and not hear, but that prophecy was not connected to a period of time when God would turn to the Gentiles. That connection is the secret or mystery later revealed, that blindness in part happened to Israel until the fullness of the Gentiles.
Les explains that Isaiah definitely said Israel's table would be made a snare, and that they would be blind and having ears would not hear. But Isaiah did not associate that blindness with a period of time when God would turn to the Gentiles. Instead, it was a secret kept in God's mind, a mystery now revealed: blindness in part has happened to Israel until the fullness of the Gentiles be brought in. Les teaches that this blindness is not forever but for a segment of time. It ends when the body of Christ is filled, the last person saved, and the church is removed at the rapture. Then God will pick up where He left off with Israel, and their spiritual blindness will come to an end as they again have a spiritual relationship with Jehovah God. Jesus also referred to such 'untils' in Matthew 23, where they would not see Him and He would be moved from their midst and return to glory.