Zelda is the princess. Link is the dashing hero (a term I use lightly) who battles to rescue and aid her. This formula should not be broken. What if someone wanted a female Mario or a male zelda. The characters are destroyed. Link shall always be my main man.
I like the idea of play-able female characters as a lead character in the future Zelda games (but not female Link). But, i doubt it will happen though...