Huh, had a thought. While yeah, this is painful to watch and all, but Sam and Dean are nowhere near over. Wherever they go from where they stand, they will go with the other in mind. Sam's hate for Lilith is about Dean, which makes is so tenacious and Dean has always been about Sam. In a way they are still on the same side. :) I think they will reconcile, in the end. They love each other too much to allow even the Apocalypse to drive them apart for long.