The age of the Gentiles is NOW! This Gospel age, or Messianic Age when not only Jews, but also Gentiles come into the Kingdom by grace through faith and the power of the Holy Spirit. This was the mystery that had been hidden in past ages, that Gentiles of faith too would have everlasting life in Christ together with Jews of faith. In past ages this mystery concerning Gentiles of faith throughout the world was not known. It was believed that God was God of the Jews only, and to have life everlasting one must be converted and become a Jew if they desire to have everlasting life. With the advent of Christ coming in His Kingdom the Gospel is not limited to Jews alone, but to whosoever of all the nations of the earth (Gentiles) shall believe Christ.
Romans 16:25-26 (KJV) Now to him that is of power to stablish you according to my gospel, and the preaching of Jesus Christ, according to the revelation of the mystery, which was kept secret since the world began, But now is made manifest, and by the scriptures of the prophets, according to the commandment of the everlasting God, made known to all nations for the obedience of faith:
Ephesians 3:3-6 (KJV) How that by revelation he made known unto me the mystery; (as I wrote afore in few words, Whereby, when ye read, ye may understand my knowledge in the mystery of Christ) Which in other ages was not made known unto the sons of men, as it is now revealed unto his holy apostles and prophets by the Spirit; That the Gentiles should be fellowheirs, and of the same body, and partakers of his promise in Christ by the gospel:
Ephesians 3:8-9 (KJV) Unto me, who am less than the least of all saints, is this grace given, that I should preach among the Gentiles the unsearchable riches of Christ; And to make all men see what is the fellowship of the mystery, which from the beginning of the world hath been hid in God, who created all things by Jesus Christ:
Colossians 1:25-27 (KJV) Whereof I am made a minister, according to the dispensation of God which is given to me for you, to fulfil the word of God; Even the mystery which hath been hid from ages and from generations, but now is made manifest to his saints: To whom God would make known what is the riches of the glory of this mystery among the Gentiles; which is Christ in you, the hope of glory:
1 Timothy 3:16 (KJV) And without controversy great is the mystery of godliness: God was manifest in the flesh, justified in the Spirit, seen of angels, preached unto the Gentiles, believed on in the world, received up into glory.
According to Paul when the last Gentile comes into the good olive tree with Jews of faith, that is how "all Israel shall be saved." Not an ethnic people, but all people of God whether Jew or Gentile. In Christ there is no difference, all believers are of the ONE same body, the ONE same faith, saved by grace through faith by hearing the Gospel in the power of the Holy Spirit.
According to John this mystery of God will be finished when the seventh angel begins to sound, and there should be time no longer.
Revelation 10:5-7 (KJV) And the angel which I saw stand upon the sea and upon the earth lifted up his hand to heaven, And sware by him that liveth for ever and ever, who created heaven, and the things that therein are, and the earth, and the things that therein are, and the sea, and the things which are therein, that there should be time no longer: But in the days of the voice of the seventh angel, when he shall begin to sound, the mystery of God should be finished, as he hath declared to his servants the prophets.
IOW the seventh angel begins to sound after the thousand years have finished, because the Kingdom is complete. There will be no more time given this earth for proclaiming the Gospel and building. Then will be time for the fiery judgment of God upon all the earth.