The Gentiles will be blessed with the Holy Ghost. Through the Holy Ghost, those who are Gentiles by lineage can become members of the house of Israel when they receive the ordinances of baptism and the laying on of hands. They are thereby adopted into the house of Israel and will be entitled to all the blessings promised to those who have the blood of Israel in their veins. Joseph Smith explained how the Holy Ghost makes this transformation.
Joseph Smith
"for as the Holy Ghost falls upon one of the literal seed of Abraham, it is calm and serene; and his whole soul and body are only exercised by the pure spirit of intelligence; while the effect of the Holy Ghost upon a Gentile, is to purge out the old blood, and make him actually of the seed of Abraham. That man that has none of the blood of Abraham (naturally) must have a new creation by the Holy Ghost." (Teachings, p. 149-150).
Therefore, once a Gentile has had this transformation take place, he or she is entitled to the blessings of the members of the house of Israel. The prophecies of Isaiah concerning the house of Israel can be likened unto them. They will be a part of the great gathering of Israel, as the Savior explained:
'But if they will repent and hearken unto my words, and harden not their hearts, I will establish my church among them, and they shall come in unto the covenant and be numbered among this the remnant of Jacob, unto whom I have given this land for their inheritance;
And they shall assist my people, the remnant of Jacob, and also as many of the house of Israel as shall come, that they may build a city, which shall be called the New Jerusalem.
And then shall they assist my people that they may be gathered in, who are scattered upon all the face of the land, in unto the New Jerusalem.
And then shall the power of heaven come down among them; and I also will be in the midst.' (3 Nephi 21:22-5).