1. Something spurns GRRM to decide to lock himself in a room and write the last two novels.
2. He learns what NOT to do from the TV series and writes and climax and denouement worthy of the books that preceded them.
3. (and this is where it gets very wishful, but I could see the money grab being worth it) HBO buys the rights to the last two books.
4. HBO decides to produce a "branch" from Season 7 (or maybe even a bit earlier) onward.
5. They hire some very talented animators (thinking things like in AniMatrix or Love Death + Robots, or some other awesome animators as I don't really like "anime".) and they proceed to produce the "Literal Ending" of GRRM's books.
6. They hire the same actors to do the voices, they produce 2, 3 or 4 seasons of this literal ending.

It's something that I don't think has been done before but I think from a $$$ perspective, it could be worth it.

It will probably never happen.