Nick tweeted out the title of book four, asking us to "prepare" our "mind, body, and soul"!!! This seems to confirm that the final season of Korra will focus on her recovering and finding balance in herself after having been emotionally and physically devastated by the Red Lotus.
Also Bryan Konietzko reblogged the news on his tumblr with the word SOON. With book four in post production are we maybe going to get a fall season of Korra? All I know is I'm more excited about how Korra's journey is going to end.