No he hasn't. He knows how he wants it to end, but there are constant changes on how he is going to get us there. For example, just recently he changed the storyline of a character in the books that is dead in the show to give them a big part to play. Before that he wasn't planning on doing much with that character. He does have several projects, but he knows now that he HAS to finish this one and #7, so he is putting it on hold, but with his writing style (1. being a slow writer and 2. him not having a real skeleton) really makes it take a long time, not to mention his constant changes he wants to do, and where he wants to put each chapter.