I think the NHL needs to step in and put in a clause saying "If for two (or three) consecutive years the attendance of a team is below X % of the maximum capacity of their home arena, and not ending the fiscal year with an account balance of zero or above, that team will be moved."
However, the big question would be "where"? There are some owners out there that have the money to subsidize their losses, unfortunately, they won't have to now that the league has revenue sharing in place.
In the end, it should be the owners decision on weather to move the team or not, and then the NHL for approval. And lets face it, we won't ever see an NHL team MOVE to Canada, maybe one might pop up in a future expansion bid, but not one will move. Bettman would rather see the NHL struggle in souther markets, as he seems to have fears of success in the north.