Among NHL-insider circles, it is apparently a foregone conclusion that the 2013 Winter Classic will be hosted by Detroit.
The article linked here states that the NHL would love the opportunity to break 100k at the Big House, although hosting it there means sharing some of the revenue (and that isn't something in which Mike Illitch may be interested), so the event could still end up at Comerica Park.
Regardless of the final location, having the Red Wings host the Winter Classic can only be a good thing. They also mention a 'hockey celebration in Michigan' to go along with the GLI. Keep our fingers crossed for a Big House Winter Classic!