It breaks my heart that we leave Cass looking so sad and hopeless. But at the same time I like it; In the beginning of season 13 we got to see Dean totally heartbroken and depressed about Cass being dead. I think we will see Cass like that in the beginning of season 14, mourning Dean and dealing with the loss. It’s clear parallells and it will be a huge part of the exploring of Destiel.