The previous verse notes that the Gentiles will repent. During the same time, the record of the brother of Jared’s vision, which showed all of human history (Ether 3:25) will come forth. This statement refers to some future event when the revelation of the entire human story as God sees it will be manifest.
Nevertheless, as we await that end-time prophecy, God promises that faith will continue to effect miracles: “Then will I manifest unto them… all my revelations.” Just as faith allowed the brother of Jared to see Yahweh’s purposes (as well as Yahweh’s person), so will the Saints in Joseph Smith’s day (and our own) be able to receive these visions of the kingdom. Indeed, the process of the restoration of the Church and the great doctrines of the kingdom revealed through Joseph Smith are a direct witness to fulfilling much of this promise. However, even though Joseph Smith fulfilled it, we should not consider it completed. The promise is that faith will continue to be effective in communicating with God. Even though great things have been revealed, the Lord promises that he stands ready to reveal more, predicated on our faith.