Goodell says it may be a possibility. I'm not crazy about this idea. If they show the game at the regular time in the States - 5:30 p.m. - that's already 11:30 p.m. in London. It's bad for the fans there and the players. If they started the game at 7:30 p.m. London time, that would be 1:30 p.m. here. That's pretty early for a Super Bowl game and it wouldn't be in prime time.
I've always thought Honolulu would be a good place for the Super Bowl every once in a while. If they are looking for sites outside the U.S., Mexico City or Toronto would be good places too and wouldn't mess up the time of the game.