There will be a Team in London. That will be the beachhead for growing the NFL into Europe. 250 million potential ticket holders. They will most likely be based in the states on the east coast and Travel to London for home games. Toronto would take away from the Bills market so I don't see that happening, they also already have a CFL team. With the growing popularity of American Football in Europe, there could come a day when they are a completely seperate but affiliated league and the Superbowl would become and international event.
We will be getting the next team or teams. Won't be an expansion. I expect the Rams to come back and either the Chargers or the Raiders sharing the new stadium with them.
How many Bills fans are there really in Toronto anyway? I mean, it's only a two hour drive away but it still involves crossing an international boundary. A completely unscientific survey conducted by myself shows that there are 18,000 people in Toronto who have "liked" the facebook page of the Pittsburgh Steelers, and only 17,000 fans in Toronto who have liked the facebook page of the Bills. The Sabers and Maple Leafs make due despite the closeness. It's still further than DC and Baltimore. And I would imagine that the NFL could complete with the CFL.
The way I look at it is that it's a huge jump to go from an entirely American based NFL to a European/American NFL. Canada would be a test to see if an NFL team can sustain a fan base in another country, and if it can, then consider London. I would also imagine that NFL players would be more inclined to live in Canada anyway, given the proximity to the United States. I'm not saying that Toronto is where an NFL team would have to be located, but it makes the most sense, given the success of other American sport teams there and because it's the largest city in Canada. Montreal would be another option, also a large city, but then you get into the issue of having a language barrier between fans and players and players not wanting to live somewhere where they don't speak the language.