User blog comment:KillRoy231/Any predictions?/@comment-2605:A000:122A:408A:ECA6:99AC:6F61:6B0B-20180330201248

I can't seriously predict anything because I can never guess where the writers are going to go, so here's one tongue-in-cheek. Let's say, based on Dabb's/Singer's recent comments, that the boys go to the alternate universe and discover that they are only half brothers. (John obviously had Adam, so...)  Michael could use Adam as a vessel in Season 5 because Adam and Dean were full brothers. Now he can use Dean.

Or they discover that Dean is actually an orphan because his hunter parents were killed when he was an infant (or his parents were killed when Mary couldn't save them). That would explain John's assigning Dean to protect Sam.

That would certainly allow the characters to evolve.

Or maybe Gabriel, now hunted by everyone because Ketch gives him (or he steals) the archangel blade when Ketch frees him, needs to hide, so Dean agrees to act as a vessel to get close enough to Michael/Lucifer to kill him/them.