Why hadn't the time to reach the Gentiles come by Acts 3?
The time to reach Gentiles had not come because God had not yet revealed that phase of His plan. Israel, the favored covenant nation, was to be the instrument to reach the Gentiles, but Israel was still dragging its feet. Peter and John understood Jesus only as Israel's Messiah, not yet the fuller scope.
Les explains that God has repeatedly kept secrets and reveals truth only periodically. At Acts 3, Peter and John still did not understand what God would accomplish through Christ's death, burial, and resurrection. They knew He was the Messiah, the Son of God, proven by miracles, but they saw Him as being only for Israel. God had not blanked the Gentiles out of His thinking; He intended to use the favored covenant nation to reach pagan, idolatrous Gentiles at the appropriate time. But Israel was dragging its feet, so that time had not yet come. Deuteronomy 29:29 confirms the secret things belong to the Lord.