If there had been no interruption, what could have happened right after the tribulation?
Had there been no interruption, the tribulation could have come immediately after Israel's rejection and crucifixion of Christ. Then Christ could have returned, set up His kingdom, and Israel could have gone out to evangelize the Gentiles. This was the hypothetical sequence the Old Testament prophets foresaw as one continuous flow.
Les explains that the Old Testament prophet did not see an interruption; he saw everything coming one thing right after another. He emphasizes hypothetically that the tribulation could have come right on in, Christ could have returned, set up His kingdom, and then Israel could have gone and evangelized the Gentiles. Because it was interrupted, the heavenly wonders did not occur right after Pentecost.