If you're a Game of Thrones fan, you know that one of the subplots involves Melisandre's belief that Stannis Baratheon is the reincarnation of the legendary hero, Azor Ahai. The books emphasize that subplot to a greater extent than the series. With the death of Stannis, it's pretty clear that he's not Azor Ahai, and... who else is left but Jon Snow?
So perhaps in some sort of parallel to Danaerys's survival of her husband's funeral pyre, we're headed toward the very dead Jon Snow, arms crossed on his chest clutching his sword, set ablaze... and coming back alive not as "Jon Snow" per se, but as Azor Ahai.
The evidence for this theory would be a cross between what would turn out to be exceptionally manipulative statements by the showrunners that Jon Snow is dead, and the fact that Kit Harrington has been repeatedly seen around the Game of Thrones set, including observation of his participation in a massive battle sequence. Let's be honest: if he's in a massive battle, it's not going to be a flashback.
It's not entirely clear what it would mean for Jon Snow to become Azor Ahai, save for it being difficult to believe that it won't come across as corny. Also, as popular as the show is, I don't think that its necessary to manipulate the audience to create buzz.