Nickelodeon have said that they may be releasing Book 2: Spirits of the Legend of Korra in February 2013. That may just be the trailers for Book 2 they haven't officially announced full details. Hopefully it will be out soon as we are crrently in March. :)
The Legend of Korra - 2012 Skeletons in the Closet - 1.11 was released on: USA: 23 June 2012
The season finale of the Legend of Korra, Book Two: Spirits, premiered on November 22, 2013.
The Legend of Korra: Book 2 - Spirits will begin airing on Nickelodeon in the United States in September 2013.
Season 2 of The Legend of Korra was called Book 2: Spirits and the release date was September 13, 2013.
there is no book 4 however, they are working on Avatar: Legend of Korra
Sadly, two years
The Legend of Korra - 2012 The Southern Lights 2-2 was released on: USA: 13 September 2013
Well as I know and find out is The new seriese the legend of Korra will Have Two (2) books only and the book 1(Air) Have 12 chapters and and book 2 ( don't know what will be about) will have 16 chapters and I don't know if they will change Their Mind or Not cuz the director is pretty creepy first he make his mind to make book 4 but after that he changed agin...,,,, we miss Ang :(
The Legend of Korra - 2012 The Sting 2-6 was released on: USA: 11 October 2013
The Legend of Korra - 2012 Peacekeepers 2-5 was released on: USA: 4 October 2013
Yes, Mako and Korra will be together in Season 2.
The Legend of Korra - 2012 A Leaf in the Wind 1-2 was released on: USA: 14 April 2012