Thanks to Studio Mir on their facebook page, we now know that the animation for Book 3 Change is complete!!! mir
"we finished animating Book 3 but we are not sure about Nick schedule. Thanks!"
We all know that animation is not the last stage in the production on a book of Korra, but it is a very good sign to see that the animation is done on all episodes. Meaning that based on all other production updates at most all that is left is colour correction and music on the last few episodes. But mainly it seems like everyone working on the show is just waiting on Nickelodeon to make a decision on when to air Book 3. They also responded to a question about the release date, confirming again that they do not know, but that they suspect that it will be soon.
 "we do not know when it will be released but it will be pretty soon!"
At this stage I find it very difficult to really predict when we will get the next big Book 3 update (Trailer or release date) I feel like they probably will do the reveals at SDCC, but that seems too far away given all of these positive production updates. Thoughts on when Book 3 is coming?