There's no trailer yet, but in the latest Famitsu, they have some updated information on the roster in Hyrule Warriors, and Fi, Link's assistant/sword spirit in Skyward Sword, is playable. You know, her:

The article also states that Ghirahim is in the game, but didn't specify playability. The same article also notes that there will be alternate costumes for Link and Zelda based on their Skyward Sword looks.

EDIT: And here's a trailer for Fi!

She's got some fancy kicks.

FFFFUCK YEAH. Unlike most people, it seems, I really liked Fi. She was one of my favorite parts of Skyward Sword... which I really enjoyed as a whole. This is awesome.

I'm really curious to see how she fights, given her status as a sword spirit and lack of arms.

One of the neat things about these Hyrule Warriors character announcements is it helped me realize that there are a surprising number of women in the Zelda universe.

Though, I would be shocked if Tingle didn't end up being a playable character.

I'm thinking of the bits where she absorbs the sacred flames and starts pin-balling around the room as a burning death sphere. Also, dancin', and it'd sorta make sense to me if she could pull out some Skyward Strike nonsense, being the sword's spirit and all. I'm pretty psyched about it, regardless, but it will be interesting to see.

That's a good point. But given the movesets that some of the other characters have, I'm sure it'll be flashy, no doubt about it!

She straight up turns into a sword.

Ew, why?

But more importantly: Dat Morningstar!

So I guess this is the closest we'll ever get to play AS the Master Sword in a Zelda game.

How long until Vaati appears in another game?

I'm guessing close to never.

Ghirahim is the real news here.

Really? But still no Tingle or Ganondorf? Pfft.

Ganondorf was teased in the E3 trailer.

My comment on Tingle STANDS.

I wonder if they will include her ability to walk/float across water? Also, she better have an animation with pirouettes.

I continue to be weirdly excited for this. Now where's our Skull Kid announcement?

I just know Saria is going to be the next character reveal. Calling it now!

This game is lacking some Majora's Mask love (besides that sweet ultimate attack that makes the Great Fairy bring the Moon down from the sky)

I really want to be able to play as the Goron to roll into hoards of enemies, the Zora would be pretty cool, and of course Fierce Deity

Playing as the final form of Majora would be cool too, but that will most likely be a boss

Dat ain't no groose

How about Uncle whats his face....did he have a name?

Oh, that's awesome.

I'm glad she's in because I always thought her design was super cool. The only reason I didn't like her in SS (and REALLY didn't like her) was the whole "every time you walk into a room I'm going to explain the whole puzzle"... thing, which sucked a lot out of a game I otherwise really love.

Edited the OP to include the new trailer!

Playing through Skyward Sword right now and Fi is probably my third least favorite thing (right behind mandatory motion controls and an empty overworld) about my least favorite Zelda. This announcement is not selling me on this game at all.

Well, this at least lets you play as Fi in a different context. And even if you don't like her, there's bound to be at least some of your favorites in the roster somewhere.

She's a surprisingly capable fighter for someone with no arms or eyes.

I've been pronouncing her name wrong this whole time.

Honestly, they made the chick from Twilight Princess who you give bugs to a playable character, so I also feel there's no excuse for the lack of Tingle. He can totally attack with balloons and do his weird ass dance into hordes of enemies,

Man, I am all over this game; I'm just more excited for it with each new announcement.