I think Jon's death is fully justified and inevitable in the text even some time before for the watch. He is a terrible LC for one, which is quite understandable for someone who literally 12-13, and has severely threatened and quite possibly undone the existence of the Night's Watch with his selfish actions. (I don't know how people have missed this.) He is apparently so focused on preparing for the threat of Others, but abandons that the second he has a personal reason to war south with the Boltons. A massive hypocrite and a fool, really. He has the hero's impulse, but he doesn't have a way to shape his moral compass, and ends up doing tragically stupid and careless things.

That being said, I think it's well possible GRRM is going to do something with Jon, in some form, but the showwriters have chosen to cut the content for whatever reason. Whatever GRRM does with Jon, though, I don't think he will have the political importance necessary to fulfill any saviour-of-the-world role. Whether Jon survives in some form or not, the Night's Watch is beyond fucked IMO. You have a couple thousand Widlings on the wall, less than half that for the NW crew, and the crow Tormund was closest to being 'loyal' to has either been axed or has come back as some weird entity. (Warg, Wight, Undead, or what have you.) Not to mention a possible/likely war with the Boltons, and related consternation from the Crown. Even if Stannis wins Winterfell in the books, their fate is that much more tied to the politics of the realm. Whether Stannis wins or loses, really, Jon has has irrevocably made his mark on the fate of the Watch like nobody has done since the Night's King.