I still kind of like the theory that book Bran will warg into resurrected Jon, like Bran used to warg into Hodor, lose himself in him by staying too long, and essentially live out the rest of "Jon"s life, while he is actually in the weirewood tree. This is a way Bran could become king. By literally using Jon, and all he represents politically and spiritually as the song of ice and fire, reborn from death, to get to the throne.