The problem is that the competitive scene is already significantly smaller than the user base of the game. MK9 will sell 2 million copies, but we'd be lucky if 2,000 people play competitively. Most people wil view the 1v1 as the main game, because that's exactly what it is. So when you say a tournament will be 2v2 and only 2v2, everyone who has been focusing on 1v1 will think twice about going to that tournament and the competitive scene gets even smaller.Eh, just because the main game is 1 vs 1 doesn't mean we should force ourselves into a hole. As long as 2 vs 2 has some competitiveness and an acceptable level of balance, i see no reason we it couldn't, further down the line, become standard. I mean all it is, is just another character which you can tag in, extend combos too and use assists with. It could prove itself to be more varied than 1 on 1 combat, but it could also prove to prove to be down right daft for competitive play. Time will tell i guess.
As other people mentioned, it's not out of the question to see 2v2 side tournaments. So you'll still get to play 2v2 in a competitive setting, it just won't be the main attraction.