As a Canadian-American, let me add something that gets rarely mentioned: Hockey in Canada is even more popular today than it was twenty years ago. The strong Canadian Dollar is perhaps most of the improvement in the business standing of Canadian franchises, but there are also far more sellouts, and revenue is much higher. Almost every building is sold out now, with Ottawa, at 99% capacity, being the lone exception. Twenty years ago Montreal wasn't even always sold out.
I'm not sure I buy that it is more popular today than 20 years ago.
Canadian teams have had a nice run, but what happens if/when some of the teams in the smaller cities (i.e. not Toronto and Montreal) go through a prolonged playoff drought? Go back and look historically--when Vancouver and Ottawa struggled, they didn't do as well at the gate.
What happens if the Canadian dollar recedes to 1990's levels?
Let's keep in mind that even a city like Quebec City is not large by American standards. The MSA has a population of approximately 765,000. Compare that to Portland, one of the smaller markets in the US that has been discussed which has a MSA population of 2,260,000. That means, for a team in Quebec to succeed, it starts out needing a vastly higher percentage of people to be interested in supporting the team.
This is why I laugh when someone makes a statement like "LA isn't a hockey town." Who cares? It doesn't matter if only 10% of the population cares about the team, that's still more than enough to make it economically viable.
The reality is that maybe Quebec can be successful. If so, it is one of the last Canadian markets that can. After that you have to start canibalizing from the Leafs in Ontario because teams in Halifax or Regina do not make sense for a major professional league.
Let's not forget, the league has always been dominated by the U.S. markets going back to the Original Six. While Canadian teams have done well at the gate in the regular season, part of hockey's recent economic success is the success of teams in large metropolitan markets in the post-season--Chicago, Boston, LA.