I can't help but wonder about Maggie's prophecy. She said the VQ was "the little brother".
Sandor is a little brother, too.
I can't remember what page we discussed it on but we fleshed that one out quite a bit. There's some theories as to Sandor fighting UnGregor at some point (maybe as champions in Ceresi's trial) and that's what will do her in.
That's also a theory that it could mean little sister instead of little brother and Arya could be the one that does it.
All kinds of good crackpot stuff.