The author says that while he hasn’t written it yet, he is hoping to achieve what J.R.R. Tolkien did with “The Lord of the Rings”: “It ends with victory, but it’s a bittersweet victory.”
Has Martin said too much (or too little) for your liking?
No. That definitively tells you nothing.
I think it means that ,probably tyrion is winning the war. ~Kidding~