One aspect of Baseball that stands out from the other major sport leagues in this nation is the playoff system. A team has to be a good team to make the playoffs since only 4 teams from each league get into the playoffs, not 50% of the league like a few other sports.It was a huge deal the last time a Wild Card team was added to the season, and I think that was a good idea when you think about it. Expanding playoffs from 4 to 8 teams didn't diminish the talent in the playoffs too much as there is enough talent to field 8 good teams, as long as each division is strong. Plus, the league was expanding over time in the amount of teams that made it up.
However, baseball now wants to add two more Wild Card teams, one for each league, and then have a play in game, or a best of three series to get the actual Wild Card Spot. This only becomes a viable addition to the post-season when there are several strong teams pushing for the Wild-Card spot at the end of the season, then this Wild Card game or series could be exciting (think of the story lines).
The main problem for this new system comes when the league is dominated by four teams. When a league is dominated by four teams, that fifth team diminishes the playoffs. If that team somehow has a better day than that other Wild Card team in that play-in game, then all of a sudden the playoff field gets that much weaker. There are also two other smaller issues. First, this could cause, especially if its a best of three, extra rest for the other playoff teams. We have seen in the past teams with too much rest falling apart in the playoffs, plus the season would have to be shortened otherwise the season would almost always go into November (unless started in March). Finally, this just reeks of greed. Generally, the teams that just miss the playoffs if they didn't make it are big market teams.
Overall, right now there is no need to add extra teams into the Playoff system. So just don't do it.