So the Phantom's confirmed as well. Likely an AT, but I thought about two other possibilities:
1) She looks like she's controlling it. It's a new move for Zelda. Sheik is gone; Zelda's new Down-B is to conjure a Phantom.
2) (And this is the most mind-blowing one.) There were actually TWO character reveals today, but we'd never know it. That's a Toon Zelda move, much like how she possesses a Phantom in Spirit Tracks. It actually looks a LOT like the Phantom she possesses...there are different types of Phantoms in the game, but the one in the pic most closely resembles her Phantom...
Note the color, designs, etc. The sword is different, but the sword shown doesn't seem to match any Phantoms we've seen so far. Doesn't have the eyes, either.
Go back and look at the pictures under Zelda's page. There might be a connection there.
Unlikely, but possible. Would be extremely clever and funny of Sakurai if #2 turned out to be true.