I think that the new Jerusalem could very well be the perfected Church:
The perfected Church is the Bride of Christ by the grace of God and having faith in Christ Jesus as being the head of His Church (body of Christ), Ephesians 2:8-10, that Jesus comes back for on the last day, John 5:28-29; 1Corinthians 15:51-58; 1Thessalonians 4:13-18. They are those who have made themselves ready as they have overcome everything this world could do to them trying to steal their faith, 1Peter 5:8.
Rev 21:7 He that overcometh shall inherit all things; and I will be his God, and he shall be my son.
Rev 21:8 But the fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death.
Once we are caught up to Christ and all things are finished after final judgement God will renew the heaven and the Earth in what scripture says ushering down the new Jerusalem. In my own eyes I see this as being the garden of Eden in how God wanted it to be as in the beginning as we dwell with God and Christ Jesus for all eternity.
2Pe 3:10 But the day of the Lord will come as a thief in the night; in the which the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up.
2Pe 3:11 Seeing then that all these things shall be dissolved, what manner of persons ought ye to be in all holy conversation and godliness,
2Pe 3:12 Looking for and hasting unto the coming of the day of God, wherein the heavens being on fire shall be dissolved, and the elements shall melt with fervent heat?
2Pe 3:13 Nevertheless we, according to his promise, look for new heavens and a new earth, wherein dwelleth righteousness.
Rev 21:1 And I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea.
Rev 21:2 And I John saw the holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband.
Rev 21:3 And I heard a great voice out of heaven saying, Behold, the tabernacle of God is with men, and he will dwell with them, and they shall be his people, and God himself shall be with them, and be their God.
Rev 21:4 And God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any more pain: for the former things are passed away.
Rev 21:5 And he that sat upon the throne said, Behold, I make all things new. And he said unto me, Write: for these words are true and faithful.