With King's Landing destroyed and Jon not wanting the throne, there's only two likely possibilities.
1. Daenerys Targaryen, First of Her Name
2. The Seven Kingdoms regain their independence.
Something that the books but not the show made pretty clear was that Westeros is currently more stable and peaceful than it ever was as multiple kingdoms. The area between the Reach, the Stormlands, and Dorne was a march constantly facing invasion or attack. The Crownlands as well was a no-mans-land constantly being invaded. The North and the Vale were also at each other’s throats over the Sisters. The Riverlands has been invaded at times by the Stormlands, Westerlands, Vale and most recently conquered by the Iron Islands, who would also raid up and down the coast. With the major exception of the North, I think most of the Westerosi nobility understands that things are better as is and would want the Iron Throne to continue on.
Things weren't exactly quiet under the Targaryens in the books. If Daenerys is gone, then even if they are still alive, Drogon, the Dothraki, and the Unsullied have no particular reason to stay in Westeros. (I could even see Jon flying off on Drogon, never to be seen in Westeros again as a possible ending.) The North has the only sizable body of Westerosi soldiers right now, but Jon doesn't want the throne and Sansa is in favor of devolution.
I suppose Jon could be guilted into taking the throne (if they can find it in the ruins of the Red Keep) but he's unlikely to leave heirs. (For that matter neither is Daenerys.)
Poll
