There will not be a lefty mode because it would delay the production. They would have to create two seperate models for Link to accomodate lefties and righties, along with the same animations, but flipped. Nintendo thought that it would just hinder the production of the game, so they decided not...
I don't think they would put the time, effort and money into making a left handed option, which is a shame because left handed gamers will find the controls too akward and not be able to play the game.