Legend of Korra: Book 2 News - 16.3.13

At the Korra panel at Momocon, the guests (Amon's VA Steve Blum, Sifu Kisu (martial arts master), and Sifu Rodriguez (consultant for Toph)) were present for a Q&A session. There they revealled that Kisu actually knew who Lin Beifong's father was and that season two will involve a new subsection of airbending being explored. Whether the new bending style will be akin to metalbending or something more sinister like bloodbending, remains to be seen.

http://avatarthelegendofkorra.wordpress.com/2013/03/14/book-2-of-the-legend-of-korra-will-reveal-a-subset-to-airbending-as-well-as-the-identity-of-lin-beifongs-father/

Two days later, the new airbending and news that Lin's dad will be revealled were confirmed, though not necessarily for season two.

http://avatarthelegendofkorra.wordpress.com/2013/03/15/subset-for-air-bending-and-identity-of-lin-beifongs-father-confirmed-for-the-legend-of-korra-but-not-book-2/

Finally, Book Two has no official release date yet, despite post-production having just starting to wrap up fairly recently. This is more down to Nickelodeon than the creators of the show though. Ah well, when it comes it comes.