The prophetic nature of the sealed section is the very reason we do not have it. Nephi declares that it is "because of the things which are sealed up" that the book must be withheld until after the time of our "wickedness and abominations." Nephi makes no more clear statement than this about the time when we might be given the material in the book.
Certainly the unsealed portion of the Book has already come too us in the time that we were prepared to receive it. The continued delay in receiving this sealed section suggests that the "people" upon whom the timing depends might be the entire world. The condition when the entire world will be past its wickedness and abominations is descriptive of the end of time. Since Nephi's future history also includes some events from that ultimate triumphant return of the Messiah, it is most likely that the sealed section will not be available to us before that time.