As for Jon, I think he will survive, either Mel the Red Witch will heal him, or she will resurrect him like Thoros did to Cat. His skinchaning abilities could be useful in controlling the dragons. He could communicate with them, or maybe even control them. Too bad he doesn't have the fire-resistance that Dany has though.
This again??? First the wights are vulnerable to fire, we know that... but the Others?? Where does this come from?? They can be killed with obsidian and that's all we know so far. As for Dany and the dragons, we have no idea how they behave during winter, in snow, they could be useless (there are theories about this, and this may be one of the reasons why the Valyrians never went North). And the thing that annoys me the most is this idea that Dany is invulnerable to fire. She is NOT!! GRRM has said it, it was a one time thing, the blood magic protected her. She has a little tolerance to heat, maybe from her Targaryen genes, but no more, fire will burn her.
Actually we don't know much of Rhaegar and Lyanna, they could have done anything during that year. It is possible they did indeed marry. Probably he kidnapped her from around Harrenhal, and we already know a septon by name that wandered that area for 20 years: septon Meribald. Even so, I don't think it will matter as I don't see Jon fighting for the Iron Throne. His double nature, Stark and Targaryen may help him against the Others but not politically.
Edited by Bayard, 11 December 2012 - 03:41 PM.