Adam Clarke on Hosea 1:10

Yet the number of the children of Israel - God had promised that the children of Israel should be as the sand of the sea. See Gen 32:12; Rom 9:25, Rom 9:26. And though for their iniquities he had thinned and scattered them, yet the spirit and design of his promise and covenant shall be fulfilled. An Israel there shall be. In the place of the reprobated people, who were now no longer his people, there shall be found an Israel that shall be the children of the living God. See the above scriptures, and 1Pet 2:10. This must mean either the Israelites after their conversion to Christianity, or even the Gentiles themselves converted to God, and now become the true Israel.