You’re asking me something only God knows. I don’t know the answer, and neither do you. However, can tell you what I surmise.
Time would not have stopped at the border of the Confederacy. Technological advances in farming equipment would have continued, and maybe would have accelerated. I suspect planters would have jumped on the chance to have mechanical farm implements that did not have to be clothed, housed and fed, and needed fuel only when working.
Here’s one situation that makes me believe they would have ended it. Near the end of the war, Jefferson Davis sent Duncan Kenner to Europe with the offer to free the Confederacy’s slaves in return for recognition of nationhood by Britian and France. It came too late in the war to do any good, but it does serve to prove there was a willingness to give it up in exchange for political independence.
When northerners abolished slavery, they managed to rid their states of most of their black population. If something similar could have occurred in a free South, it’s very likely the Confederacy would have abolished slavery.
There were other circumstances that I believe would have led to the end of slavery. What I do not buy are ludicrous claims made by people like Diane Roberts who has said if the South had won, blacks would still be slaves today.