Nephi is not only predicting Christ’s appearance to the Nephites, but is noting that at that time there will be a change made in the law that will govern their lives. This is the prophesied end to the law of Moses that the Nephites are to keep until that time. Nephi is therefore very clear on not only the person of Christ, but on the meaning of Christ in the fulfillment of the law of Moses. He looks forward to the day when Christ will provide new law.
It is not clear whether or not this prophecy of Nephi was widely available to the Nephites. It is certain that Lehi’s prophecy of the birth of the Savior in 600 years was know, because it is used against the believers. However, the context of that section refers to Samuel the Lamanite as a source, and not Nephi (see 3 Nephi 1:4-6). This prophecy does not appear to have been repeated at any point in the available writings of the later Book of Mormon prophets. The Samuel prophecies would have been more recently in mind, and the lack of mention of Nephi does not necessarily prove that the small plate tradition had virtually disappeared, but it is quite suggestive that it had.
The absence of reference to this prophecy of the replacement of the law of Moses was either not available to those future generations because the transmission lines of the small plates tended to keep them from view (Mormon finds them only after searching through the records he is working on) or we simply don’t have the references because they were not part of what was selected to be entered onto the plates. The general neglect of the authors and traditions of the small plates does create a legitimate argument that the tradition had disappeared from the main line of Nephite religious thought.