I understand that the Civil War was essentially fought over slave ownership and that slavery represented the cornerstone of the Southern economy, but surely their leaders would've realised that sooner or later it would have to be abolished?
Were there any ideas or suggestions that slavery could eventually be abolished had they turned out successful in the war?
No. The leaders were so far from thinking it would have to be abolished someday, that in their constitution they forbade there ever being any law outlawing slavery: Article I Section 9(4) "No bill of attainder, ex post facto law, or law denying or impairing the right of property in negro slaves shall be passed". They also put in their constitution that all states, including new states added later, must allow slavery. The belief at that time by those people was that slavery was a positive good; they quoted Bible passages showing why it was just; and all in all argued that it was the right thing to do.
God no. Every document concerning the confederacy essentially enshrines the practice of chattel slavery.