The very last section of Chapter Fourteen is about what Lincoln does after his assassination and vampirization (totally just made that word up). He and Henry continue to fight for black civil rights (by killing Ku Klux Klan vampires, for instance) and go to Europe to fight the vampires there during World War II, which was yet another vampire war.
But we hear all of that in very short lines of summary, like, "They'd been there in Mississippi, dragging white-hooded devils to their deaths by the light of burning crosses…." (14.31). That's all the info we get about Henry and Abe fighting KKK vampires (which could be a whole other book itself). In fact, we're not even 100% sure that's what that line says. Are the "devils" really vampires? Or are Abe and Henry actually just killing KKK members?
And when we hear about them fighting the "second vampire uprising between 1939 and 1945" in Europe (33), we don't hear about who the vampires were or what they were trying to do. Though our hours of watching the History Channel lead us to assume that the Nazis were the evil vampires. Is that not right?
We could see these lines as setting up all the sequels and spin-offs that Grahame-Smith will write when he runs out of other mash-up ideas. But we could also look at all of these lines and think about what they all have in common, which is the idea that Abe and Henry had lots of work to do in fighting off the vampire menace. In fact, the ending says exactly that: "But there was still work to be done" (34).
Now, this "work" that Henry and Abe have ahead of them might be fighting vampires. But vampires are associated with racism and other forms of inequality, so maybe Abe and Henry are just off fighting for equality and against racism, vampires or no. This might explain why they were watching Martin Luther King, Jr. give his famous "I Have a Dream" speech. (To be fair, they could just want to hear MLK's shout-out to the Emancipation Proclamation.)
After all, Henry and Abe still have a lot of work to do; and this is just what Martin Luther King, Jr. says, too—that he will not be satisfied "until justice rolls down like waters and righteousness like a mighty stream." In other words, the dream of total equality hasn't yet come true, and it'll take a lot of work to make it a reality. That's why seeing white and black kids playing together is a dream of his, and not just his afternoon picnic plans.
But here's the weird thing: at the end of the book, we don't hear about what happens to Abe between 1963 (Chapter Fourteen) and 2008 (when Henry gives Abe's journal to the narrator in the Introduction). So, where's Abe? Why does Henry have his journal? And what happens with the narrator?
If we could check back in with Seth Grahame-Smith, we might get some answers, but alas, he's busy writing Unholy Night.