[Smithy]

To paraphrase the very elaborate theory, the book of Revelations features a seven headed dragon (the Targaryen dynasty ruling over the Seven Kingdoms) who is eventually brought down by an opposing army (Robert's in this case). In the aftermath of this, a pregnant woman flees and gives birth to a child (Lyanna Stark), a child who is prophesied to rule over all nations (Jon Snow). The child is then spirited away by a giant bird (House Arryn's sigil is a falcon, and Jon Arryn was the foster parent of Ned Stark).

Meanwhile, two dragon-like beasts rise from the sea to rule over mankind (likely Dany and Aegon conquering Westeros from across the Narrow Sea), causing fire to rain down on the land (Dany's dragons). Finally, a savior arises, with the people rallying behind him (according to this theory, Jon again).

Here's where things get really crazy though. In Revelations, this savior leads an army of riders clad in all white. According to the theory, Jon will turn to the Others to reclaim Westeros (perhaps even becoming one), eventually triumphing over the Targaryens, but losing himself in the process.

Revelations ends with the messianic figure reigning for a thousand years, leading this theory to conclude that an immortal Jon Snow will take the Iron Throne, ruling over a shattered Westeros in a very bittersweet ending.