Writing Forum

That is one of the things I love the most about the "Song of Ice and Fire" series, its intricate plot, and the way it is filled with details about subplots one might not even notice the first time around.

Though, G.R.R.M. actually describes himself as a pantser (he calls it a gardener), having only some of the major plot elements planned out. So it is definitely possible to write amazing plots without outlining. Of course, this could very well be one of the reasons why he takes such a long time writing each book. I imagine he ends up changing quite a lot from the first drafts. Furthermore, he has more than forty years of experience writing professionally, so he has probably developed some excellent instincts about story structure.
Finally, it is quite possible that he mentions prophecies and other forms of foreshadowing in one book not knowing how to fulfill them until later. If you listen to the writing excuses podcast, you will sometimes hear Howard Tayler mention that people sometimes thinks he is brilliant for foreshadowing events years in advance in his online story, even though it was not meant to be foreshadowing at the time.