It comes full circle. Those who were lost have returned again. The "prodigal" will return. (Luke 15: 11-32.) There will be joy at the return.
This will happen as a preliminary to "the gospel of Jesus Christ [being] declared among them." The Gospel being declared requires a true message, true messengers, authority, and ordinances. That will follow the remnant receiving the Book of Mormon. To what extent the gentiles bring those things and to what extent it will require heaven's direct involvement, remains to be seen. But when the remnant reconnects, they will reconnect in every respect. The "gospel of Jesus Christ shall be declared among them!"
As a result of these events, the remnant "shall be restored unto the knowledge of their fathers." What does it mean to be restored? What knowledge? Which fathers? The Nephites, and Lehi, or to the earlier "fathers" as well? Does this include Abraham, Isaac and Jacob?
What does it mean they will be "also [restored] to the knowledge of Jesus Christ?" What does this "knowledge" involve? What kind of relationship with Christ does this imply?
If we wonder at the "knowledge" the remnant will obtain, we have a parallel given to us: The future remnant knowledge of Christ shall be akin to that "which was had among their fathers." Meaning they will grow to know what the earlier Nephite disciples and peoples knew. What kind of knowledge does that include?
When the right target receives the right Gospel, the results are dramatic. When the wrong group is entrusted with the Gospel, they tend to let it atrophy, grow dim, and become a social order without the power of godliness. The restoration was intended to cure that problem. But as with any gift from God, we must do more than to "take no thought but to ask." (D&C 9: 6-7.) We must pursue knowledge and act with alacrity when it is given.
If we do not do this, then the result is not a blessing, but a cursing. (D&C 124: 47-48.) No matter what we are offered by the Lord, we must act consistent with His will to receive the blessings offered. When we fail to fulfill the obligation He appoints to us, then we fail to obtain what was offered. (D&C 124: 31-32.)
Once they have been given the gospel, the remnant will not fail. Their reconnection will be as a nail in a sure place, not to be moved. Their knowledge will grow into the perfect day, just as it might with anyone who is willing to receive what Christ offers. (D&C 50: 24.) Noon at the summer solstice is a symbol of the perfect day. This year, in contrast, at midnight of the winter solstice there will be an eclipse. This would be a symbol in the heavens of the opposite of the perfect day. When it arrives it undoubtedly is a sign relevant to the time. (Those things are never accidents or mere happenstance.)
The ideas begin to accumulate. Darkness and light. Free will and acceptance of what is offered by God. So many divergent roads that are offered in place of the one that remains strait and narrow, but nevertheless in a straight course before you. (2 Nephi 9: 41.)