You and I might be the only ones who would like to ponder that one. It is an interesting thought.
No one supports slavery - we always have to make that disclaimer if you are from the South - but why if the South was so inherently evil and so ignorant, and had the right to secede (Lincoln said so), and slavery was legal - didn't they let them go. If I had a member of my family that was just rotten to the core, but legal, and they wanted to leave - I would hold the door for them.
You and I might be the only ones who would like to ponder that one. It is an interesting thought.
Make that three....
I wonder if slavery would have faded out on its own after several more generations. After all, many of the top leaders of the Confederacy had an ambiguous (at best) view of it (Robert E. Lee) or believed it was a temporary measure needed to bring the blacks up to civilization (Jefferson Davis, for example, who also gave hunting rifles, as gifts, to some of his slaves).
Also, industrialization was somewhat slower in the South than the north, but it likely would have increased in time, which would have lessened the demand for slaves.
And if this had happened with many interests still in common, it's possible that the Union and Confederacy would have re-united somewhen along the line.
Just one path of speculation.