First announced on the 2 hours long special Sword Art Online extra edition that aired today (12/31/2013). The arc covered will be of course the Phantom Bullet arc, one that in my humble opinion is the best the series has to offer.
Here is the promotional Video
The official website was also updated with the news
My wish for new year is, please just don't take Sinon/Shino role away from Miyuki Sawashiro :)