As long as there are groups willing to pay north of one billion dollars in expansion fees, there will be revenue.
Seattle and Vegas have been a boon for HRR with sellouts, increasing sponsorship and merchandise since they came into league.
Sports Franchises are increasing exponentially in value, The Senators sold for 950 million, with the possible exception of the Coyotes, other franchises will sell for more. Per Tim Graham, there are brokers who represent people who are hungry to buy franchises, there is demand.
The NHL depends on attendance more than any other league, it will never be in the same tier as the other leagues in terms of television deals.
The leagues total TV revenue per season is actually closer to one billion when the 433 million from the Sportsnet Deal is added onto the 625 million from ESPN/TNT. Putting teams in Houston and Atlanta would mean the NHL is in the Top 15 Areas in terms of the population in the US. Getting this done has the potential to dramatically increase the value of the next US TV Deal, especially in light of the new streaming package which will allow ESPN and TNT to be purchased together. The money will be there for expansion.