Could the Civil War have ended without the freeing of slaves?

The question of whether or not the Civil War could have ended without the freeing of slaves is based on many what-ifs and speculation. However, it is important to gauge how critical slavery was in the cause, continuation, and results of the Civil War. 

Despite his personal beliefs against slavery, President Lincoln was initially willing to let slavery remain at the cost of reuniting and preserving the Union. The Confederates had many chances to rejoin the Union and maintain their slave trade. If one of Lincoln's initial offers had been accepted, slavery may have very well continued in the South; entertaining a theory of an early Southern victory allows for too many theoretical possibilities, however. As the war progressed,  it became apparent that the  longer the war dragged on, slavery would become an even bigger issue. Lincoln made one final offer of acceptance, the Confederate states were given 100 days to surrender and come back and slavery wouldn't be touched. Again, the Civil War could have ended here and slavery would still be allowed to continue.

Frederick Douglass said: "Any attempt now to separate the freedom of the slave from the victory of Government; any attempt to secure peace to the whites while leaving the blacks in chains will be labor lost." Douglass was concerned that the North and South might end the war with a settlement that would allow slavery to continue. He wanted to make sure the issue of slavery defined the war and that a Union victory would result in the end of slavery in the US. 

Personally, I believe that the Civil War was fought for the protection of slavery, and there was very little room in the hearts of the Southern slave-holders for a peace without GUARANTEED freedom for slavery. I mean, did the South really think that if they came back, things would go back to normal and ALL slave trade could resume as before? No. Therefore, the Civil War was to be fought for the abolition of slavery (even if the North did not use it as a rallying cry in the early years of conflict). The Civil War played to the idea of abolition even before it became about the freeing of men, particularly after the releasing of the Emancipation Proclamation. After this transformation of cause and motivation for the War, I don't think that it could have ended without the freeing of slaves.