Once we find out what Joseph's strawberry-shaped birthmark really means, the story ends pretty quickly. We already know deep down that Joseph's a gentleman, so it should be no surprise that the newly revealed heir of Mr. Wilson "remains blest with his Fanny, whom he doats on with the utmost tenderness, which is all returned on her side" (4.16.20).
Oh, yeah, and Fielding does have to get in one last dig at Richardson: he tells us that Joseph will not be "prevailed on by any booksellers, or their authors, to make his appearance in High-Life" (4.16.20). What the heck? Well, that's a reference to Richardson's authorized sequel of Pamela (yes, this massive, 600-page snooze-fest—according to Fielding—had a sequel), which chronicles her pregnancy. Scandalous. Another guy, John Kelly, wrote a similarly named sequel, Pamela's Conduct in High Life.
Pamela is just the gift that keeps on giving, but Joseph Andrews… well, Fielding says it's better to stop while you're ahead.