The idea that some of the guys are not used to this weather because of playing at Florida is overblown. As has been repeated here, Hernandez and Gronkowski are from Bristol, CT and the Buffalo, NY area respectively. More importantly, they've been playing and practicing in New England cold weather for two months. Ditto the Bears. Neither team will be unprepared for the cold or snow.
The fans argument might have merit, except that I'm sure mass transit will still play a large role in bringing fans to the game. Chicagoans are as used to the snow and foul weather as we are. I expect to see near 100% capacity.
In short, the weather angle is a little overblown, except in the effect it will have on the passing and (especially) the kicking game.
EDIT - Pats rookies born in cold weather areas now included in my signature.