Re: Jon/Varamyr warg thoughts
I don't see him claiming Ghosts body, he is too important to the story to be killed off (HAH, Going to eat these words!).
His brothers stab him to the point they think they've killed him, they quickly run out and sound the cry blaming Wun Wun, and all hell breaks lose. I see the watch in shambles next book, because Jon was the only thing holding the wildings and the crows together. I expect Tormund takes over the wall (they outnumber the queen/nights watch easily) and holds it honorably, and Jon is restored eventually (though he has probably been spirited away by Mel as they are fighting).
As Jag said, he'd go into Ghost - but as Imp said, not for long. I expect he'll be unconscious next book in a brandream/wolfdream for his first chapter, but not dead.