Would only take some dodgy franchise move to do this though, e.g. a current east team moves to the west. The NHL could have kept the old format with a reshuffle of two teams but decided to change it loads more for some reason; what's to stop this from happening again? I hope it doesn't expand too much more than what it is at the moment, I feel the exclusivity would be lost slightly.
At least at this moment in time, it seems like all the franchises, outside of Phoenix, seem to be fairly stable. Could be a problem in the future but I'd be surprised to see a relocation outside of the Coyotes happen within the next decade. Plus, I'm sure the NHL would try to keep relocations as close as possible geographically, sort of how the Coyotes almost went to Seattle. Just speculating here but say expansion happened and the Coyotes had to move, perhaps Las Vegas would be an option since they'll have the new arena and it wouldn't affect the divisions at all.