How does San Jose do when the team isn’t doing well? The Sun Belt teams have difficulties when their teams struggle. I only mention those cities because they have a long standing passionate fan base. The NHL isn’t going to contract anyway so this is all conjecture.
SJ is usually in the playoffs, plus the fan base includes a lot of youth league and adult rec players. Hockey is huge in SJ.
One problem is that there are only nine teams with really strong fan bases ... and by this I mean teams that will draw 15,000+ fans to a late-season game even if the team is out of playoff contention. These teams are the "Original Six" (New York Rangers, Montreal, Boston, Toronto, Detroit and Chicago), plus Philadelphia, Buffalo and Edmonton.
Buffalo is borderline because it's a city in decline, but it's got a great core of fans and some great regional rivalries. Edmonton may be the most hockey-crazed city in North America, but it's a small city by major-league standards and had a winning tradition in the 1980s that it will never match again.
Take these nine teams and add another nine that cover large metro areas in the U.S., teams with strong winning traditions, and a couple of mid-sized markets in Canada ... and you've got a good core for the NHL. I would consider these nine possibilities:
10. St. Louis
11. Los Angeles
12. Ottawa
13. Vancouver
14. New Jersey
15. Pittsburgh
16. Minneapolis
17. Denver
18. Washington