It is not the NHL owners job to grow the game.  Their investment is theirs alone.  What are NHL rights worth in China?  Korea?  Russia?  Europe?  The games are played outside of the hours they would be seen in those countries.  
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They already have all of the best players in the world.  Expanding the league so they could play around the world would further dilute the talent per team.  Maybe the NHL could own a chinese league?  That happens with or without Olympics.  So what exactly is the upside?