Spoiler alert for Game of Thrones and A Song of Ice and Fire beneath the cut. I have to share something with someone and ask limits suck. Seriously, don't read if you don't want a major fucking spoiler.
So that's the first part of this theory. The second part has to do with Daenarys' dragons. During the books, the phrase "The Dragon has three heads" is repeated. Daenarys is obviously the first head of the Dragon, and we see in the 5th book how much difficulty she is having managing three dragons. There must be one Targaryen for each dragon. The reveal in Dance with Dragons that Aegon, son of Rhaegar and Elia, brings the second Targaryen into the open. That means we need one more, and I think it must be Jon.
But Jon is tied to the Night's Watch! Except the Night's Watch oath reads as follows, "Night gathers, and now my watch begins. It shall not end until my death..." Jon's oath ended when he died at the end of the 5th book. That means that he can now be free to do whatever he wants. And it has already been shown that Priest/priestesses of Azhor Azai can bring people back from the dead (i.e. Thoros of Myr and Beric Dondarrion). So Melisande can bring Jon back from the dead so he can go be free to become the last Targaryen.
Now, the real enemy of the books, which everyone seems to forget about, are the motherfucking White Walkers. And nothing seems to be able to kill them, except FIRE! Who has fire? DRAGONS.
