melisandre (in the show) even met thoros of Myr and learned about the resurrecting powers of the lord of light.... so ... it's so obvious he's coming back... remember that melisandre said the promised hero is said to wield a flaming sword named Lightbringer.... since we know that beric dondarrion's blood lit his sword on fire we can presume jon will now be able to do the same after he comes back....only that in this case longclaw does not get damaged by fire since it's valyrian steel....thus fulfilling the profecy of the flaming sword that will not only will be able to kill the white walkers but also the wights (which can only be killed by fire).... besides.... he needs to die in order to become "the prince that was promised" the one rhaegar targaryen said his was the song of ice and fire... since jon is the son of rhaegar targaryen (fire) and lyanna stark (ice) he is the one true hero.... heir to the iron throne and will lead the battle against the dead....BUT he is a very honorable man as well, as was his father... therefore, dying is the ONLY way Jon gets released from his Night's Watch vows------- "Night gathers and now my watch begins. It shall not end until my death..."
