Ephraim will cease to be a people in 65 years:
This occurred in the twelfth year of Ahaz. But that the Israelites remained in Samaria, and kept up the forms of a civil community, and were not finally carried away until the time of Esarhaddon, is evident; compare 2 Chronicles 34:6-7, 2 Chronicles 34:33; 2 Chronicles 35:18; 2 Kings 23:19-20. Manasseh, king of Judah, was taken captive by the king of Assyria's captains 2 Chronicles 33:2 in the twenty-second year of his reign; that is, sixty-five years from the second year of Ahaz, when this prophecy is supposed to have been delivered. And it is also supposed that at this time Esarhaddon took away the remains of the people in Samaria, and put an end to the kingdom, and put in their place the people who are mentioned in Ezra 4:3. (Barnes' Notes on the Bible - Biblehub.com https://biblehub.com/commentaries/isaiah/7-8.htm)