A summary of 2 Nephi 29 is that the new revelation divinely granted to Joseph Smith confirms Christ intended to confirm the Nephites under the wing of the Jewish blessing and lineage. And John 10:16 and Matthew 15:24 are used in justifying that belief.
John 10:16 – And other sheep I have, which are not of this fold: them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd.
Matthew 15:24 – But he answered and said, I am not sent but unto the lost sheep of the house of Israel
So, there must be others included in God’s plan for salvation other than the Jews.