I know its far to early to listen to what he says but I can see why he'd consider hanging them up.
Next year he has this road schedule:
Chicago Bears, Detroit Lions, Green Bay Packers, Philadelphia Eagles, Washington Redskins, New Orleans Saints, New England Patriots, New York Jets.
One indoor the rest outdoor and cold and potentially tough games with good defences (Pack, Eagles, Jets, Pats, Saints, maybe Skins, Bears).
This year was perfect for him.
Soft schedule, one cold weather game all season, lots of nice arenas for him to play indoors.
He's an old man coming off another bruising NFCCG defeat. If he can't get it done this year with everything in his favour, next year doesn't look promising.