KJV: 28 Be it known therefore unto you, that the salvation of God is sent unto the Gentiles, and that they will hear it. 29 And when he had said these words, the Jews departed, and had great reasoning among themselves. ”
NIV: 28 Therefore I want you to know that God’s salvation has been sent to the Gentiles, and they will listen! ”
ESV: 28 Therefore let it be known to you that this salvation of God has been sent to the Gentiles; they will listen.”
CSB: 28 Therefore, let it be known to you that this salvation of God has been sent to the Gentiles; they will listen.”
The added verse smooths out the transition between vv 17–28 and the summation of the book in vv. 30–31, in essence repeating the content of vv 24–25.