The most obvious interpretation of this verse is that the house of Israel will someday know that the Lord has not forgotten the covenants made to their fathers (v. 15). These covenants are not completely fulfilled until Christ’s Second Coming when Jerusalem and Zion are redeemed. Therefore, when the Lord says, then shall my revelations which I have caused to be written by my servant John be unfolded in the eyes of all the people, he is referring to the Second Coming, when all the dramatic and glorious things spoken of in the book of Revelation will be brought to pass and made manifest in very deed.
However, we should not assume that John did not write more. The Lord specifically referred to his revelations (note the plural form). It seems likely that the Lord had reference to other unrevealed writings of John the Revelator when he spoke of great and marvelous things which have been hid up from the foundation of the world (v. 15). This too, like the vision of the brother of Jared, is yet to be revealed.
Neal A. Maxwell
“Many more scriptural writings will yet come to us, including those of Enoch (see D&C 107:57), all of the writings of the Apostle John (see Ether 4:16), the records of the lost tribes of Israel (see 2 Nephi 29:13), and the approximately two-thirds of the Book of Mormon plates that were sealed: ’And the day cometh that the words of the book which were sealed shall be read upon the house tops; and they shall be read by the power of Christ; and all things shall be revealed unto the children of men which ever have been among the children of men, and which ever will be even unto the end of the earth’ (2 Nephi 27:11). Today we carry convenient quadruple combinations of the scriptures, but one day, since more scriptures are coming, we may need to pull little red wagons brimful with books.” (A Wonderful Flood of Light, p. 18)
Hugh Nibley
“John enjoys a special place in the Book of Mormon, where he is the only future prophet mentioned by name. His special office, however, is not to serve as a prophet so much as a recorder. It is John, the man in the white robe whom Nephi sees in a vision, who is to write the fullest record of the Lord’s ministry (1 Nephi 14:19-25) and the accurate setting forth of his words as they proceeded out of his mouth, ’plain and pure, and most precious and easy to understand of all men’ (1 Nephi 14:23); but his record and those of others to whom the Lord ‘hath shown all things’ are to be ‘sealed up to come forth in their purity’ after the bringing forth of the Book of Mormon--hence Nephi was forbidden to write them (1 Nephi 14:25-26). When the Book of Mormon has been brought forth and introduced to the house of Israel, then shall they ‘know that the work of the Father has commenced upon all the face of the land’ (Ether 4:17), and when the people begin to believe, ’then shall my revelations which I have caused to be written by my servant John be unfolded in the eyes of all the people;… the time is at hand that they shall be made manifest in very deed’ (Ether 4:16).” (Since Cumorah, p. 206)