Good points. I read an article that Philly has interests in hosting a Super Bowl...if things go well in East Rutherford. SI did a polarizing article about places that in their view, should host the big game:
http://nfl.si.com/2014/01/24/eight-in-the-box-future-super-bowl-host-cities-london-seattle/
I think the drawback is that other than Metlife, the stadiums in the Northeast are pretty small compared to others in the league. Plus with Fedex Field, the field surface is a big concern over there and I read somewhere that fans have to walk a mile to the stadium from the nearest Washington Metro station. It doesn't sound much but if it's snowing and all that, chaos!
The real question is who's going to host in 2018 and beyond? The new Vikings stadium, maybe? The next three following this one are in Glendale, AZ (2015), the new 49ers stadium (2016) and Houston (2017).