What’s Up With the Ending?
It's simple, really. The end of Genesis is leading up to a sequel.
Here were are, left in Egypt, with all of God's big promises to Abraham, Isaac, and Jacob totally deferred and unfulfilled. Yet Joseph says to his offspring, "God will surely take care of you," and then makes his final request: "you shall carry my bones up from here" (50:25). It's pretty clear that there's more to come, and so we're thrust forth straight into the book of Exodus, where God (finally) leads the people out of Egypt.
Spoiler alert: even in Exodus, they still don't make it to the promised land. Looks like this might be more than your regular trilogy.