These two verses both deal with the sign of the beginning of the gathering, which is that the Book of Mormon will come forth.
[these works and the works which shall be wrought among you hereafter shall come forth from the Gentiles] When the record of the Savior’s appearance to them is revealed to the Gentiles in the Book of Mormon.
[unto your seed which shall dwindle in unbelief because of iniquity] Those now known as the Lamanites. In spite of the origins as a term of lineage, Lamanite is no longer related to lineage. The remnant of these people in Bountiful will be present when the Book of Mormon is revealed, and they are those that we term Lamanites.