mark my words - 99.9% it will be like this.
1. 7 is the number of bungo,
2. exos minds can be transferred and are probably stored somewhere as copys.
3.They don't rip their only iconic NPC out - he is money.
4. Bungo/activision love money.
5. just because they said at e3 he is dead , in a way where they garuanteed meant - at "this" point he is dead, but he'll be recovered later to keep people in the dark.
6. Its bungo, they always went with the oh he is dead or is he not type of rated t for teen story
(queen,uldren,cayde)
7. you just red 7 reasons, for cayde-7, so it's bungo - confirmed