The end of Bereishit is so anti-climactic.
Take a quick glance at the end of each other "Book of Moses," and a typical reader is very satisfied.
Shmot (40:38): A cloud rests on the Mishkan (signifying God’s presence), and a fire guards the Jewish people at night through all of their travels. In the context of the completion of the Mishkan and the continuation of the travels in the desert, this verse makes perfect sense.
Vayikra (27:34): These are the mitzvot which God commanded Moses to tell the Israelites at Mt. Sinai: a perfect summary verse of the contents of a book primarily focused on laws.
Bamidbar (36:13): These are the commandments and statutes that God commanded the Israelites through Moshe, in the plains of Moab, near the Jordan, across from Jericho. This verse also summarizes what the book is about, including the narrative and laws which bring the Israelites to the point of being a little over two months away from entering the land of Canaan/Israel.
Devarim (34:12): This verse is part of a longer statement summarizing the greatness of Moshe, and the wonderments he presided over in the process of taking the Jews from Egypt to the Jordan River. It is a perfect ending to the Torah which is named for its master teacher, Moshe.
Comes Bereishit 50:26 which tells us Yosef died at age 110, was embalmed and placed in a coffin in Egypt.
Where is the tribute to the forefathers? Where is the anticipation of the coming years? The last eight verses of the Torah portion are all about Yosef! If anything, 50:24 would have been a more suitable ending – Yosef promises his brothers there will be a redemption and God will take the Jews out just as he promised to Avraham, Yitzchak and Yaakov!
To strengthen the question, the very beginning of the book of Shmot reviews the fact of Yosef’s death (1:6), and could just as easily have mentioned that his remains were placed in a coffin in Egypt. That fact, put at the beginning of the book, instead of at the end of Bereishit, might even be a better reminder, so to speak, of the need to take Yosef’s remains with them for burial in Canaan. (Obviously, the Torah had not yet been given, but the homiletic idea of more commonly looking at the beginning of a book than the end is meant as an illustration of how things seem out of place.)
The commentaries point out a few singularities in the verse.
Firstly, it does not say he was buried.
Secondly, it does not say where the box was placed.
One common approach is that Yosef’s remains were placed in the Nile so the waters would be blessed on his behalf. (See Rabbeinu Bachya) (Baal Haturim observes that “Nilus” נילוס and “Yosef” יוסף have the same gematria (numerical value), 156.)
Another approach maintains Yosef was not buried, so it would be easy to identify and take his remains when it was time for the Jews to leave (see 13:19) (see Chizkuni and Seforno)
While the commentaries debate the nature of the coffin’s material and what its purpose was (to protect from water or other elements), perhaps the second approach, that Yosef was not buried, is what gives us the climactic moment we seek.
Consider: if Yosef is buried and hidden away, what is the point of his promise? The chances are he will be forgotten. The midrash is replete (and see Rabbeinu Bachya for more) on how Moshe had to seek to find, in order to fulfill the forgotten promise to remove Yosef’s remains from Egypt.
Some argue the Egyptians placed Yosef in the river so his descendants would not find him. But what is stopping us from suggesting the brothers made, in line with Egyptian custom, a monument or a crypt in which Yosef’s remains stand, unburied, as a reminder of his promise to the Jewish people?
For a people who are about to fall into the depravity of Egypt, a culture from which the rabbis teach us they were only saved because they kept small parts of their heritage, such as their names, language, certain secrets, and were not gossipers nor steeped in Egyptian immorality, Yosef’s remains might stand as a mainstay, as a reminder of what it means to live in Egypt as a Jew. Yosef did it by himself, with no familial support, for 22 years.
As the Jews eventually become idolaters, steeped in many Egyptian (im)morals, Yosef’s remains would be the ultimate reminder of what it means to be a wanderer who is not home, a stranger who has a better future in a different land.