In the last days, before Christ's second coming, will he unite his people who are divided into many church denominations into one body of his bride?
There is no passage in the New Testament that states Jesus has ever accepted the concept of denominations. Instead, Jesus' prayer was, "I do not pray for these alone, but also for those who will believe in Me through their word; that they all may be one, as You, Father, are in Me, and I in You; that they also may be one in Us, that the world may believe that You sent Me" (John 17:20-21).
When the Corinthians began dividing among themselves, Paul scolded them. "Now I plead with you, brethren, by the name of our Lord Jesus Christ, that you all speak the same thing, and that there be no divisions among you, but that you be perfectly joined together in the same mind and in the same judgment. For it has been declared to me concerning you, my brethren, by those of Chloe's household, that there are contentions among you. Now I say this, that each of you says, "I am of Paul," or "I am of Apollos," or "I am of Cephas," or "I am of Christ." Is Christ divided?" (I Corinthians 1:10-13). There have never been multiple beliefs or multiple churches. Only one has ever existed. "There is one body and one Spirit, just as you were called in one hope of your calling; one Lord, one faith, one baptism; one God and Father of all, who is above all, and through all, and in you all" (Ephesians 4:4-6). Either a person is a part of that one body or he is not.
When Jesus' return, it announces the end of the world. There is no other age beyond this one. "But each one in his own order: Christ the firstfruits, afterward those who are Christ's at His coming. Then comes the end, when He delivers the kingdom to God the Father, when He puts an end to all rule and all authority and power. For He must reign till He has put all enemies under His feet" (I Corinthians 15:23-25). The Bible does not teach that Christ will be reigning but that he is reigning and will continue to reign until death is conquered. At Jesus' return, all rule, authority, and power come to an end. The very world will end. "But the day of the Lord will come as a thief in the night, in which the heavens will pass away with a great noise, and the elements will melt with fervent heat; both the earth and the works that are in it will be burned up" (II Peter 3:10).
Therefore, no Jesus isn't coming to unite his people. He gave the command that they are to remain united and when he returns it will be to bring judgment on those who failed to follow his commands. That is why Jesus warned, "Enter by the narrow gate; for wide is the gate and broad is the way that leads to destruction, and there are many who go in by it. Because narrow is the gate and difficult is the way which leads to life, and there are few who find it" (Matthew 7:13-14).