According to Miyamoto in a recent Iwata ask’s session. Princess Zelda will be “pretty good” in Skyward Sword. So far there has not been any word if Princess Zelda will be a playable character in Skyward Sword. With this comment from Miyamoto makes one think she may be. If  you remember Spirit Tracks was the first Zelda game that we were able to control Zelda. Could Nintendo be planning something with Zelda in Skyward Sword?

Link