Ephraim will become a Multitude of Nations

The prophecy about Ephraim:
But his father refused and said, "I know, my son, I know; he also will become a people and he also will be great. However, his younger brother shall be greater than he, and his descendants shall become a multitude of nations." (Genesis 48:19 NASB)

The promise to Abraham:
As for Me, behold, My covenant is with you, And you will be the father of a multitude of nations. (Genesis 17:4 NASB)

The future blessings of Israel as prophesised by Paul:
For I would not, brothers, that you should be ignorant of this mystery, lest you should be wise in your own conceits; that blindness in part is happened to Israel, until the fullness of the Gentiles be come in. And so all Israel shall be saved: as it is written, There shall come out of Sion the Deliverer, and shall turn away ungodliness from Jacob: For this is my covenant to them, when I shall take away their sins. As concerning the gospel, they are enemies for your sakes: but as touching the election, they are beloved for the father's sakes. (Romans 11:25-28 NASB)

Ephraim will become a multitude (fullness) of nations (gentiles).