It was always my impression that the weather isn't such a factor for the game itself (the majority of teams play in cold-winter climates so both players and fans are used to the cold). My impression was always the associated parties and celebrity that comes along with the Super Bowl who otherwise live in a Los Angeles bubble. As well as to provide a reason for many to head south in January. I mean, it's easier to walk a red carpet in Miami than it is in New York during a January blizzard. And we'd be denying reality if we didn't say that all the A-list parties and events surrounding the game weren't a huge part of the Super Bowl.
I think the NFL will predominately continue to have Super Bowls in the South but I think they realized that every so often they're going to have to throw a bone to the northern cities who, in many cases, help fund these teams through miscellaneous development deals and/tax breaks.
The Wikipedia article states the reasons for choosing each city, but I think there's a reason why New Orleans leads in the number of Super Bowls hosted (including the upcoming 2013 game): it's a great place to have a party; especially in winter. While New York will be the first game to be held outdoors, I think that aspect will have little bearing on the ability of other un-domed, northern cities to host the Super Bowl. It will be how well the host city can throw together the whole event that will allow people to forget that they're not in Miami or New Orleans.