"Dying" is absolutely a loaded term. Anyone who has browsed a forum for an online game (such as World of Warcraft) will know that people have been complaining about their games dying for fifteen years. Yet these games continue to hum along with viable communities playing them. However, the truth of the matter is that while the games aren't truly "dead" they've often cratered in popularity as players have moved on to other interests. This can be due to a variety of factors such as shifting demographics, new games to pull attention, mismanagement from the game studio, etc. So on the one hand, a game might be a shadow of what it once was and "dying", but on the other hand people were calling Guild Wars dead back in 2007 and I still play it.
With that out of the way, yes, I think hockey is dying in Canada the same way that World of Warcraft has been dying the past 10 years. There are old heads who still play and watch hockey, but the kids these days don't. Points about demographics are very relevant to this conversation (despite it still being an impossible subject for some), but it doesn't really matter what the cultural background of the 20 year olds in my office are, white, Indian, Asian, native, black, you name it, none of them care about hockey! Everyone I talk hockey with is 30 or older, so unless a new generation picks it up at some point it will really start to die off.
The game is too expensive. Canadian teams are dogshit and interest dries up. The NHL is garbage at advertising and there's as many opinions about how to improve the product as there are posters on this site. Other sports are taking up young fan interest. It goes on and on and on, but the thrust is all the same. Canadian interest in both hockey and the NHL is a not what it once was and shows no signs of improving. Does that mean dying? I don't think that actually matters.