Most biblical scholars associate the origin “New Covenant” with Jeremiah or Ezekiel.
Scott Hahn in Kinship by Covenant cites J.G. McConville and J.G. Miller’s Time and Place in Deuteronomy in which the authors observe that Jeremiah and Ezekiel are pulling on Deuteronomy 30:6 where God promises that Israel’s heart will be circumcised. This, Hahn says, reveals that the “Deuternomic covenant is self-programmed for a future renewal – one that clearly transcends its initial promulgation – through a decisive act of God for the purpose of effecting a radical internalization of the law.” (KBC, p. 114)
This is remarkable because it shows that God’s desire to transform His people into His “sons” had not changed. The era of the Law was a probationary period until the “fullness of time” when God would bring about this plan of sonship by sending His own Son to bear the legal curses and rise up victorious from the final curse of death.
Also, Deut 32:43 seems to indicated that the nations would become “his people”. This goes along with the promise God made to Abraham that all the families of the world would be blessed through him. God’s “end game” is adopt all the nations as his sons through His son Israel, but particularly through His divine Son, the Israelite Jesus Christ.