Well, there's two possible ways it could go. I'll just start with the bad one; something that might end up like a less extreme version of the scenario found in Mumby's "Centuries of Shadow"; abolitionism takes much longer to really take off, and many of the Southern planters, wanting to retain their profits, firmly entrench themselves in the system, sometimes currying plenty of favors with London, ensuring that very little gets done for a long time to come; it may even take until the early 20th Century to eliminate slavery. And even then, race relations may remain poisoned, or at least strained, until the present day, particularly if the *South takes the Rhodesian route.
On the other hand, the Colonies may, possibly, end up more along the lines of the C.N.A. from Sobel's classic "For Want of a Nail" timeline.....which is to say, basically somewhat like a giant *Canada, of sorts. This is actually harder to pull off, I'd suspect, but the results could be quite satisfying, as well.
