Major league sports expansion in Canada suffer serious challenges (beyond Toronto, and beyond hockey).
1) - The cost of talent (players) is monetized in US currency, which gives a lot of unpredictability to operating costs due to currency fluctuations. The Canadian dollar is almost always undervalued compared to it's US counterpart.
2) - All major league sports are based in the US. The main advertising markets are in the US. Canadian cities are virtually unknown south of the border. There is very little upside for any US based league in considering Canadian expansion. US fans are uninterested in watching a Canadian team play. There are no natural intercity rivalries. This lack of interest makes selling advertising and getting TV exposure very difficult. This is a serious monetary issue.
3) - There is serious shortage of both personal and corporate wealth in Canada (at least compared to the US). Many US cities are festooned with billionaires wanting to stroke their own ego by owning a major league club. The same cannot be said for Canada. It would take many hundreds of millions if not billions of dollars to set up a new major league club in a Canadian city. Who would step up to the plate to do this???
Having said this, I could see the NBA being interested in expansion to Vancouver or Montreal. I'm sure MLB is serious about a return to Montreal. I doubt there will ever be any further NHL expansion in Canada. As for the NFL -