According to Ken Rosenthal of FOX Sports, major league baseball will expand playoffs beginning with the 2012 postseason. The current playoff system has four teams in each league making the postseason: one from each division, with a wild card in the American League and National League. Under the new system, another wild card from each league would make the playoffs, battling it out in a one-game playoff for a chance to advance to the Division Series. Instead of eight total playoff teams, there will now be ten.
Rosenthal says the deal is not yet finalized, and there are still some elements that need to be resolved. As such, specific details aren't yet known.
MLB will expand playoffs beginning with 2012 postseason - MLB News | FOX Sports on MSN
"Baseballs playoffs will expand from eight to 10 teams, starting this season, according to major-league sources. MLB will expand playoffs beginning with 2012 postseason"