This question is often asked not to learn truth, but in the spirit of a prosecuting attorney attempting to disprove the work as an obvious fraud.
It turns out that there there are three parts to the Plates of Mormon, which were translated into the Book of Mormon, the last two of which had been sealed. Part 1 was always unsealed and became the Book of Mormon. Part 2, being the first sealed section, contains several books to be translated by the seer Mauricio Berger. Part 3, the majority of the plates (see illustration), is the second sealed section, which contains the "Vision of All", which will be opened by the Savior. By the way, the Sealed Book itself also states at the last sealed section will not be opened before the Savior comes to His temple Zion (Words of Moroni 21).
So the answer is that the Sealed Book does not contain the Vision of All. It is contained in the portion of the gold plates which still remains sealed.