Bob Costas has made that suggestion because of the success of the wild card teams in the playoffs. The idea is since the team didn't win their division, it should be more difficult for the wild card team to win. Having 2 wild card teams facing each other to play in the divisional round using their best pitchers, would put them at a disadvantage going into the 'first round'.
I do see the point but Selig has dismissed it. Of course going to the current format with 3 divisions in each league, their worst nightmare is the San Diego phenomena. You'd think if they did go to a 2nd wild card team it could raise the level of play in the playoffs, especially this year.