User blog comment:FTWinchester/Who's still watching?/@comment-1149167-20140419081244/@comment-5619706-20140419105451

I feel like the only way the show could end is if they permanently kill Sam and Dean. Death stressed in Season 6 how important it is not to meddle with supernatural affairs. If you don't kill one who is supposed to die, somebody else will. I feel like it parallels the story of Sam and Dean and the show itself. Sam and Dean will always find a way to stay together, even if they mess up the natural order for a shitload of people. Everytime they do that, something crappy happens, and as long as they have that unhealthy relationship, it would never end. At this point, it was probably better to have just let the Apocalypse take its course.

Additionally, the show itself tried to keep Sam, Dean and Castiel alive to pander to the fangirls, but in effect, something else had to die (and that is the lore/story). In many ways, Appointment in Samarra speaks volumes on what happened to this show.