User blog comment:SeraphLucifer/Discussion/@comment-79.115.74.88-20151118180644/@comment-9249716-20151118221336

Gabriel being killed happened years before hey got to this point, and the show doesn't have Kripke as he head writer even though he's in charge of producing it. I think the writers wanted I bring him back because of fans but were mostly teasing in that season 9 episode before they officially confirmed it, we just don't know that he actually would side with metatron (I highly doubt he would choose metatron considering who Gabriel sided with in season 5).