Helaman 15:11

yea, even if they should dwindle in unbelief, the Lord shall prolong their days until the time shall come which hath been spoken of by our fathers, and also by the prophet Zenos, and many other prophets, concerning the restoration of our brethren, the Lamanites again, to the knowledge of the truth;

Even if they stop believing, the Lord will let them live longer. This will last until the time our fathers spoke about. The prophet Zenos spoke about it. Many other prophets did too. They told about our Lamanite brothers coming back to know the truth.

Even if they drift away from faith, the Lord will preserve them until the time our ancestors spoke about—the time the prophet Zenos and many others prophesied about—when the Lamanites will be restored to knowledge of the truth.