My prediction: Gendry ends up as king.
And no matter what happens to Jon Snow (but he probably gets killed in a falling out with Daenerys), Arya kills Daenerys.
I don't think there is going to be a King or Queen of the Seven Kingdoms when this is over. King's Landing is destroyed, and there literally is no longer an Iron Throne. I think it'll just go back to being seven Kingdoms rather than The Seven Kingdoms.
No idea what is going to happen with Danaerys. Arya killed all the Freys, she killed the NK, so to have her kill Danaerys as well seems like...overkill? (pun intended). I could see nobody killing her, and her simply returning to Essos where she is loved rather than staying in Westeros where she essentially is hated.
Kind of curious what happens with Tyrion, though. Truth is, nobody actually
knows that Cersei is dead, and they
should learn that Tyrion freed Jaime. And, Jaime and Cersei very nearly did escape King's Landing. So, I'm wondering if Danaerys could go full paranoid, believe that Cersei may have escaped and still be alive, and so seek to punish Tyrion.