Playoffs teams if 4 wild card playoff system had been in place
2011: Red Sox (90-72; 1 GB), Braves (89-73; 1 GB)
2010: Red Sox (89-73; 6 GB), Padres (90-72; 1 GB)
2009: Rangers (87-75; 8 GB), Giants (88-74; 4 GB)
2008: Yankees (89-73; 6 GB), Mets (89-73; 1 GB)
2007: Tigers (88-74; 6 GB), Padres (89-74; 1 GB)
2006: White Sox (90-72; 5 GB), Phillies (85-77; 3 GB)
2005: Indians (93-69; 2 GB), Phillies (88-74; 1 GB)
2004: A's (91-71; 7 GB), Giants (91-71; 1 GB)
MLB appears close to adding 2 wild card teams this season, with the two wc teams in each league having a one game playoff. One stated reason for doing this is that there has not been enough of an incentive for teams to win their division if they are cruising to the wild card anyway.
That sounds like a worthy goal, but that is not always realistic even under this new system. For instance, way back in 2011, the Yankees had a huge lead in the AL East (won it by 6 games) and the Wild Card was going to come down to the collapsing Red Sox and the surging Rays. The Red Sox were desperately trying to win the wild card and avoid ignominy. The final dash to the wild card produced one of the most exciting nights of baseball ever, capped off by Evan Longoria hitting a walk off home run against the Yankees after Jonathan Papelbon blew a save against the Orioles minutes earlier.
Under the new proposed format, those games wouldn't have mattered much (except for home field in the one game playoff), and the Red Sox would have grabbed one of the Wild Card slots after their historic collapse. That's only one example where doing this to make winning the division more important would not have worked.
In this example, the new format would have allowed an undeserving team in the playoffs without making the division title more important. Of course, there are other examples where the new system would make a difference (such as in 2010 where the Yankees and Rays were tied for the division going into the final game and no one else in the race for the Wild Card).
That does not mean that adding two new wild card teams is completely without merit. There will be plenty of positives as well as negatives. The one game playoffs would often be thrilling, and two additional teams (maybe teams that haven't been the playoffs a lot) would get their chance at getting to the World Series. We would learn to love it, or at least accept it.
It will be controversial if second place wild card teams that are 6 games back win these games on a regular basis. Most people, though, love an underdog and won't complaint too much if the Yankees or Red Sox are that first place team. Based on that last 8 years, that scenario is much more likely in the American League, where the second place wild card team was at least 5 games back in 6 of 8 years, while it never happened in the NL.
Turning it into a three game series might make it more fair, with the "better" team being less susceptible to losing in a fluky way. Adding three games could make scheduling the playoffs a nightmare, especially now that they want the World Series to end in October. It also might be too big of a punishment for not winning the division (especially when the wild card teams might have a better record than a division winner). It will work itself out, but you have to hope that this is the last playoff expansion they have in mind.