Because I honestly don't see them raising the level cap for a bit. Maybe I'm wrong... But it just doesn't seem like a logical thing to do at this point in the game. Should fix the game up until this point and keep max at 50 before they introduce stuff associated with a new cap. I see a level cap increase around the time they release for PS3.

They're also trying to make some endgame raids - raising level cap means they gotta go back and re-balance for the new max.