Is a true "Supernatural" fan surprised at all? Sam and Dean have died literally a hundred times, and have managed to come back (there were a lot of demon deals, magic, luck, and God involved). Now the fandom would be surprised if any of the major characters do die and stay dead within the show's lifespan. According to Misha Collins himself (his tweet managed to reveal everything we need for hope and tons of speculation) and Jared Padalecki, who accidentally released the spoiler during one of the conventions, Castiel will be making a comeback.
Season 12 recap
Although we all witnessed the horrible, and heart-wrenching death of both Castiel and Crowley (possibly Mary, but in "Supernatural" you cannot even take death for granted), now we get to watch Castiel come back to life for the second or third time (I lost count). How cool is that? Fans are also speculating that the Castiel we saw get killed by Lucifer, was actually the version of Castiel of the other realm, but with "Supernatural" the options are infinite.
How we found out?
According to Misha Collins' tweet, fans should not lose hope, because Castiel does have a future. There are no more details from him, though on how that future will look like. Maybe Castiel will be revived by the Jack; however, there is no way of knowing from now, what method of vivifying the writers have chosen.
Misha Collins actually was fair to the fans and warned them for the gravity of the situations that would occur in the last ten minutes of the season 12 finale. He went on to state that the fans should expect to be shocked, and devastated (as if the other season finales have been easy on our poor and fragile hearts).
Season 13 expectations
Andrew Dabb stated that season 13 is not necessarily the last season of the show and that "Supernatural" will go on as long as the fans remain invested emotionally in the story line. Furthermore, Andrew Dabb said that season 13 will take the characters in directions that we have not seen yet. We already know one of those story lines, and it is as weird as "Supernatural" gets.
Apparently, the boys will be featured in an animated episode alongside the Scooby Doo gang. We expect a lot of weirdness from this TV Show; however, it never ceases to surprise, and amaze us at the same time.
Season 13 of "Supernatural" is being kept under wraps; however, nothing can escape the attention of nosy fans (basically the whole fandom). Bringing back Castiel, or whatever version the writers decide, is a move that will have half the fandom screaming in joy, and half murmuring: "I knew it!"
