Obviously He was presenting something that had always been because He told Nicodemus this: "Art thou a master of Israel, and knowest not these things?" If it was something new, why would Nicodemus have been expected to know it?
Amen Brother, God doesn't change:
Jesus Christ is the same yesterday and to-day, yea and for ever. Heb 13:8
Concerning the OP:
But the Jerusalem that is above is free, which is our mother. For it is written, Rejoice, thou barren that bearest not; Break forth and cry, thou that travailest not: For
more are the children of the desolate than of her that hath the husband. Gal 4:26,27
I amplify:
....For more are the children of the desolate [the Gentile fold] than of her that hath the husband [the Jewish fold]
Those referred to in Ps 87 that are of Rahab, Babylon, Philistia, Tyre, and Ethiopia that were born in [the heavenly] Zion are examples of the children of the desolate. God always has had a people from every nation under heaven.
I suggest to you that when Peter made this exclamation in Acts 10:
“......Of a truth I perceive that God is no respecter of persons: but in every nation he that feareth him, and worketh righteousness, is acceptable to him”
.........there wasn't anything new about that either.