If there were to be even numbers in each league; there would be three solutions. 1) Play a full season of inter-league games 2) Retract two teams 3) Add two teams
1) Play a full season of inter-league. I know some people who would like to see this. But, I wouldn't expect it to happen any time soon. Baseball purists already dislike the idea of the inter-league as it is.
2) Retract two teams. Ok, which two? Rays = 1. They can't draw a crowd, even after going to the World Series, and their stadium sucks. But which team gets the 2nd axe? Marlins? Nationals? No, they each have new stadiums. Pirates? Once again, new stadium, plus no way would they get rid of one of the classic teams, plus Pirates fans will go to games, if they can get a damn team worthy of watching. So who??? Exactly, there really isn't a good 2nd option, especially with so many newer stadiums having been built, locking teams into leases and contracts and whatnot.
That leaves us with option #3....add two teams. The beauty is there would really be no change in playoffs. There wouldn't be a Wild Card, but there would only be 4 teams in each division. Expansion has its risks (see: NHL, Krispy Kreme), but with risk comes reward. The NFL successfully runs 32 teams which it can do because of wild popularity of the sport. One reason NFL can get away with it though is the limited number of games. With 8 home games (not including playoffs), each game is a holiday of sorts. Can it work with 81 games? Depends what market you move to. So, where exactly:
Orlando:
Ok, with the recent ridiculousness surrounding Orlando by a politician and a TV journalist. Orlando getting a MLB team is a current topic. Here's the thing Orlando, what makes you think you can fill a stadium, when your friends 1 hour away in Tampa aren't putting any asses in seats, not to mention the ballhawker heaven that is Landshark Stadium with the Marlins attendance woes (new stadium in a better location will help). Sorry Orlando, dreams don't always come true, but keep wishing upon that star.
Omaha:
I don't know, why I would say Omaha....why not though. They host the College World Series, and ummmm have good steaks. Think about it though, aside from Kansas City, most of the plains has nothing, can't we throw them a bone? Omaha has a large population, a thriving college town nearby in Lincoln. Even Iowans can get in on the action, all they have is a slightly worse version of the Chicago Cubs...called the Iowa Cubs. ... I'm done with this thought, it won't work.
Canada:
Canada isn't a city! I know, I know. Let's break it down, and we can do this quickly. I really only envision 3 possible cities that could support a team. Montreal = Already failed. Ottawa = Too far north. Vancouver = Too close to Seattle. Thanks for playing Canada.
Buffalo:
I mean, the good folks from Buffalo deserve to have something other than the shitty ass Bills, but, I don't think this will work. They are pretty rabid Sabres fans though if I recall from my last visit there.
Nashville:
This would put the Brewers AAA team in flux. But Nashville, makes a great centralized location for a large fan base throughout Tennessee, and even Kentucky. They quickly latched onto the Titans when the Oilers moved into town.
Realistic Locations
Not too hard to imagine this. If memory serves me right, they were pretty quick to latch onto the Expos when they came to town. They are very, very avid baseball fans. I'm pretty certain they would instantly pour support for a new team. This is a very viable, and plausible option. Also would look good for the MLB in the Latin American communities. And look, they already have a stadium!
Las Vegas:
Vegas has been wanting to get a professional sports team for some time, and why not, they are a big enough city that is continually expanding. My big problem though, is most people who have moved there, moved from somewhere else and will likely continue to support their already favorite teams. Sure, they might support the Vegas team, but would they really be die-hards? Plus, you'd have to hope they wouldn't have such blind of ambition as the Cubs fans do, or else they'd be broke from betting the house.
Charlotte:
Lange didn't like this choice looking at the Hornets leaving town, the Bobcats coming and doing little better, and of everyone's favorite NHL team, the Hurricanes. I'm thinking about the success of the Panthers though, and the fact the Carolinas are big in minor league baseball. There is plenty of population that really has little else to cheer for in terms of the Major Leagues. I think it would be successful.
And now for my two selections
Indianapolis:
How does a city of this size get by with nothing more than a AAA baseball team? Talk about getting a whole state involved immediately for what one could assume to be a loyal fanbase. Ok,

Portland, OR:
Figured I better specify Oregon; I don't think the lobsterheads in Maine will switch their "Sawx" allegiances anytime soon. Yes, the lovely city of Portland should have Major League Baseball. Too far from Seattle and San Francisco/Oakland, all these poor residents have for a professional franchise is an NBA team...and no one should be forced to like the NBA. Once again, state pride would be at stake, and you'd have an instant fan base.You'd also have the instant rivalry with the Mariners. Plus with a new stadium, you could have a beautiful ballpark with a picturesque scene that the residents could, just, totally mellow out to. I mean, the fine people of Oregon didn't have their ancestors risk life, limb, dysentery, thieving bands of travelers, and poorly caulked wagons to get to Oregon and NOT have professional baseball!
This post is purely hypothetical, but if there is actually some sort of research on this topic, feel free to share. Our comment board won't bite.