Interesting discussion. A few overarching thoughts:
(1) Contraction in any league isn't realistic
(2) Personal preferences of owners matter (even if they're irrational)
(3) Stadiums (AKA corporate suites) matter more than markets
(4) Predictions (within next 5 years):
NHL: Nothing. Gary Bettman has his head so far in the sand regarding the failed Sun Belt experiment along with continuing to ignore the Canadian markets that actually watch hockey that this league will be stuck. I wish that I could say differently.
NFL: Jaguars move to new NFL stadium in downtown LA (assuming that this gets built, which is certainly not a guarantee). That's the one NFL team that really has a true need for a relocation (as opposed to, say, the Vikings, who have a bad stadium but a great fan base).
MLB: Nothing. I'd love to see MLB switch an NL team to the AL for a 15/15 balance (and I really don't care if that requires at least one interleague series going on at any point in time during the season), but you're not going to get any takers from the NL. Without a volunteer from the NL, there isn't going to be any realignment in baseball (which I personally believe is needed).
1-3 are very good observations.
As for predictions...
I agree that "nothing" will probably happen with regard to MLB's alignment. With the possible exception of the Oakland A's or Tampa Bay Rays. However, MLB really doesn't have any where for them TO GO. Baseball is THE toughest sport franchise for a city to support because of inequities in payroll and the number of games. Virtually everyone in the top 40 in US market size has massive issues in the way of getting an MLB team. Portland and Charlotte are really the only possible places to go (outside of OAK to SJ), but they also have pretty big issues.
As for the NHL, I would have a strong disagreement about your Bettman comments.
#1 - "The Sun Belt Experiment" was NOT Gary Bettman's idea. The NHL announced plans to expand to 28-30 in 1989. Four years before Bettman was named commish. Expansion teams in FLA, TB, ANA and SJ were already awarded by the time he took control. Teams in PHX, DAL and CAR were also not his idea. Those were owners who sold to be moved, and he tried to find local ownership for WIN and QUE, while the owners of MIN and HAR were hell bent on leaving their cities. They were ARENA ISSUES, not "we need to add southern markets" issues.
Bettman was in charge of awarding four expansion teams. Columbus and Minnesota are not Southern. He awarded four teams to cities that HAD NHL teams and lost them (MIN, ATL) or were teased with a relocation and didn't get them (Hartford was on tap to go to Columbus, New Jersey was exploring a move to Nashville). And he's an out-spoken advocate for a team in Winnipeg and Quebec.
He's put seven-year no relocate clauses in ALL ownership transfers since losing QUE, HAR, WIN and MIN. He's fought to keep every team in its current location regardless of destination. He made an exception to NHL ownership rules to keep the Edmonton Oilers from moving to Houston.
#2 - There's absolutely zero factual evidence to support the idea that a "southern experiment" exists or has failed. What was "experimental" about putting teams in massive markets? A lot of those teams are at the low-end of the spectrum in terms of attendance and revenue... well, no s#&%. They're also the teams with the least history, least tradition, and least on-ice success. PHX, NASH, CBJ, ATL have never made it out of the first round of the playoffs. SJ, DAL, ANA, CAR, TB all have (all five have either won the Presidents Trophy for best regular season record, OR a Stanley Cup) and are all doing quite well financially and attendance wise. FLA has made it out of the first round before, but not in like 12 years.
Furthermore, the success of the "Sun Belt Experiment" isn't measured in the revenue each team brings in individually. It's measured in "what have they done for the league." The NHL had teams where 24% of the US/CAN population lived in 1989. They now have teams were 37% of the population lives. They had a US TV contract that gave them $15 million a year in 1989. They now have one that gives them six times that amount and for a 10-year stretch was getting even MORE from ESPN.
#3 - Phoenix DOES need to move. Atlanta needs an owner and might move. It would not surprise me if nothing happened in the next five years in terms of teams and their locations in the NHL. But it also wouldn't surprise me if Houston, Quebec, Winnipeg and or Kansas City landed an NHL team, either through relocation, an expansion to 32 teams, or both.