Consider how much the NBA and NFL have grown in the past several decades; they have not needed to infuse cash via expansion franchises.
I think of such issues such as not going to the Olympics as unforced errors that has hindered hockey's popularity on the global stage. Bettman still maintains that the average fan isn't interested in the cap? Really? How out of touch can you be. Time for a change at the top.
Yeah, I can see that if NHL was in that tier then it wouldn't be needed; however NFL is just not a comp. NBA is looking at expanding however; so is MLB.
I think that the NHL has really failed to grow the game globally (Europe for sure is a major untapped market for NHL revenues) but there is much more politics involved in that compared to other sports.
The one advantage that the NHL has over the NFL, NBA, and MLB is the Canadien economic support for NHL teams. At best, the other leagues might find 3 host cities that could support a team in the NFL, NBA, or MLB (Toronto, Montreal, and Vancouver) but the NHL has 7. There are 41 "major league" markets in the USA from all the major sports leagues (not counting MLS as a major sport). So from a quick view that means there are potentially 48 viable markets to choose from and that excludes Hartford, Connecticut and Austin, TX as well as only counting single markets that can support multiple teams (NYC, LA, Toronto/Chicago, Bay Area, etc).
The difference in places like Atlanta, Houston, and Phoenix and other USA markets is that without a team there is little NHL revenues to gain from them; but placing an team there and there is massive interest in supporting a team in the NHL. Comps from minor league teams are not an indication; this is about entertainment and hockey not just hardcore hockey fans. This is why expansion can increase overall revenues because it is a gate-driven league that then supports national TV/streaming audiences. In a way, it is more similiar to soccer (non Premier League) than it is to the NFL.
So given what the NHL can actually control:
1) they can do better at growing/marketing the game within the existing footprint
2) growing the footprint (via expansion) is a great strategy as well.
These both can be done independently of one another to maximize growth.