I was re-reading the Jon spoiler chapter on Martin's website today, and this little bit struck me:
Once they had been six, five whimpering blindly in the snow beside their dead mother, and him alone, the pale one, crawling off into the trees on shaky legs as his litter mates sucked cool milk from hard dead nipples. Now only four remained of the six born that day, and one of those was lost and gone.
Which made me wonder who the "lost and gone" direwolf was. Ther four wolves in question are Nymeria, Summer, Shaggydog and Ghost (the "narrator"). At first I was thinking it was Shaggydog, since we haven't heard anything about Rickon since the end of Clash of Kings, but now I wonder if it night not be Summer. At the end of Storm of Swords, Jon makes passing reference to having no sense of his wolf after he passed south of the wall with the wildlings. Does the Wall not only protect the south, but also prevent some forms of magic from passing through, or whatever it is that the worgs and Stark children share? The only person who has been able to contact someone beyond the wall has been Bran, and we know he is special in some way.
It may not be much, or anything really, but I was wondering if anyone else had any thoughts.