The inside HBO stuff made it pretty obvious that Stannis is alive and that Jon is coming back. Neither of them got separate videos like most major events/deaths do, while Myracella got one instead.
Also, they dance around saying Stannis is dead. Lots of talk about how he was ready to die and how Brienne came to kill him, but they never outright stated he was killed unlike Myracella and Jon. They even set up why Brienne would let him live by talking about how she expected a monster but found a broken man. Its the same thing they did last year with the Hound's "death".
So for the running tally:
- To be resurrected: the Mountain, Jon Snow
- Secretly Alive: The Hound, Stannis
- Deader than Dead: Myracella, Stannis's wife, Ramsey's Lover
- MIA: Everyone on Gendry's Boat tour of Westeros
- LOL: Benjen