Jacob is addressing a long future audience. Assuming we can accept his verb tenses as representative of Jacob's meaning rather than an interpolation from Joseph Smith's perspective, The "had a hope of his glory" presumes an audience that reads these words after the birth and mission of Christ makes that a reality. Jacob declares for the purposes of posterity not only that he has a faith in the mission of the Savior, but that this understanding is the essential message of all of the prophets. Jacob places himself into this company.
We might also note that Jacob indicates that "we write these things..." At this point, he can only be speaking of Nephi. While we might impute this explanation forward in time, it is probable that this is a testimony that Jacob gives for himself, and in behalf of his brother Nephi, a man who may also be rightfully included among the prophets Jacob invokes.