Emboldened by the Holy Spirit and the resurrection of Jesus, Peter boldly speaks to the gathered crowd. In verse 39, he tells them that there has been a paradigm shift and the gospel message is not only for the Jews but also "for all who are far off" (i.e. the gentiles). Isaiah 57:19 prophesied that gentiles would be included in God's plan to bring light to the world and Peter confirms that the time is now. The second paradigm shift is that there is a move from the law and works to salvation by faith in Jesus and what He did.
Although the Holy Spirit is speaking through Peter, he still fails to understand at this point that both faithful ethnic Jews and gentiles are included in God's plan as both recipients and messengers of the gospel. This is evident in Acts 10 and in Galatians in Peter's dealing with Cornelius. God draws believers to Him by His grace and then sends them out to spread the good news of salvation by grace through faith. As in the Old Testament, God wants his children to be both separate from the world and a light to the world. Doug pointed out that as seen in the Old Testament book of Esther, non-believing ethnic Jews became believers in Yahweh because of His work in saving the Jews and they in turn were a light force in causing the conversion of gentiles.
The message God had in Peter's time and for today's generation is that Jesus Christ paid the penalty for our sins through His death on the cross and gave us the hope (i.e. a confidence that something will come to pass because God has promised it will come to pass) of eternal life through His resurrection. We are to share that message in truth and in love.