The obvious ending is Jon Snow becoming king of Westeros, as he is both Stark and Targaryen, it's literally his destiny.

However, doing that would refute the entire thesis of GRRM's series, that there is no inherent good, no destiny, no saviors, etc. He started the series with a faulty premise as a refutation of Tolkien and now he can't come to terms with the fact that that necessarily leads to a shitty conclusion