Daenerys will go mad with all the power that she has acquired in Essos, uniting all of Westeros against her when she finally arrives with her dragons and foreign horde. By this time, however, the Starks will have taken the North back from Ramsay Bolton and flayed him living as he so liked to do to so many others; rebuilt their army and recruited more giants to slay Dany's dragons with their massive arrows; and raised up Jon as their king because of all his deeds as well as what many people have surmised to be his true parentage. There will be a great battle, and despite their shared heritage, Jon will kill Daenerys and reforge the sword Lightbringer, which he will then use to defeat the Others.