I don't know about unity being restored. I am not certain that it ever existed among all of those who are to be part of the Body of Christ at the end of the road.
Perhaps between Adam and Eve in the Garden of Eden prior to their disobedience there was unity, but after that...?
Jesus came and the Holy Ghost was poured out on Pentecost to make unity a possibility, but excluding the Adam and Eve situation I don't see where it could really be called a restoration of unity. Establishing unity, yes!
"Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ:" Eph 4:13