They could be. The NBA and MLB are gearing up to hit 32. The NBA could announce it at any point, the MLB will be moving towards that once the A's and Rays situations are concrete. The MLS will join the NBA and MLB next year with 30 teams, ironically enough in San Diego. The NFL, depending on who you ask, is either fine with 32 teams or looking to raise it to 36 with an "international division". All four will be watching the NHL if they go beyond 32, which is the most likeliest league to expand first.