A lot of the traditionalists and purists would argue that MLS tries as hard as it can to go away from the world order of how pro soccer leagues are supposed to be administrated. They're not happy with playoffs at the end of the season and no promotion/relegation.
I've even heard rumblings from traditionalists in the soccer blogosphere that they think MLS is absurd for trying to introduce instant replay technology on its own.
But, what really gets the purists irked is how the league has grown itself past the exact, measured amount of teams that are supposed to play in a league. World leagues are not supposed to be more than 20 teams according to these supposed experts.
On this one point, I think MLS may try to mend things with those worldly soccer know-it-alls. I hypothesize that the MLS end game is 40 teams, two 20 team conferences. MLS can achieve a few things with a 40 team, two conferences league. Automatically, they can explain how important it is for them to have 20 team conferences to conform to world type standards. Their excuse for two conferences is an easy one to explain. The country with Canada is too big for only 20 teams.
What two conferences of 20 teams also does, is set the schedule straight. This puts them on target for a 38 game season, just like the other world leagues. Or, if they want to do an MLB interleague thing, they can add ten games for a 48 match schedule. Every year, those 10 games can be switched out for different interleague competitors.
Obviously, the two winners of the conference playoffs can face off in the title game (MLS Cup).
The single most important reason for why the league needs to get to 40 teams is to spread its brand. There is still an emptiness for MLS when it comes to Tv ratings. It struggles mightily in getting a television audience.
The 'big 3' of football, basket and baseball (MLB, the NBA, the NFL and college football) are still dominating at high levels. MLS will still have troubles establishing its prominence with casual sports fans with 28 teams, which is where they have already claimed they will be in a few years.
But, with 40 successful teams, there may not be a way to deny the league of its presence in American and Canadian culture.
Now, the fun stuff, speculating on which metro areas will have teams. This is how I see it:
2 teams in NYC area
4 Florida teams (Miami, Jacksonville, Tampa, Orlando)
Raleigh or Nashville (neither has an MLB team)
Detroit, Pittsburgh, Baltimore, Milwaukee, Cleveland or Cincinnati (take your picks)
3 teams in Southern California
3 Bay Area/Northern California teams (including Sacramento, San Jose)
4 Texas teams (Dallas, Houston, San Antonio, Austin)
Salt Lake City
My prediction is that MLS will hit 40 teams around 2033.
And, the good news is that even with a first division of 40 teams, there is still plenty of room for a solid second division.