… already married, (we) have two sons called (Mako and) Bolin.
They bring us no small amount of joy and…
much trouble. I believe you (formal and plural) can understand…
(I/We) hope that one day you (formal and plural) and them can (meet) each other …
On top (is) our photograph.
Notes: Chinese has two ‘you’ 你 (ni) and 您(nin). 您 is formal, similar to the German “Sie”. That their father uses it with his family can have two meanings, either it is a show of respect (in the past it was normal to address one’s parents that way) or it means they are distant, which, considering that he left after a big fight, is also a possibility. These days 、您is not used with one’s family anymore, but a show of respect to your boss, elders, your Professor or customers.
Book 3 will be the first 13 episodes of season 2 (season 1 comprised of Book 1 with 12 episodes and Book 2 with 14).
Studio Mir will animate ALL of Book 3 (and 4).
Book 3 begins a “few weeks” after the events of Book 2. source
Metalbending Police chief Lin Beifong and her family will play a large role; "We’ve got great stuff planned for Lin and her family. It’s not right away, so don’t be mad if it doesn’t happen right away. Book 2, for the Lin fans…she’s not very heavily featured in Book 2, BUT, very heavily featured in Book 3" - Bryke during a book signing. source
Thematically, Book 3 is about "Korra dealing with the change of the world in this point in time. At the end of Book 2 she says it’s a new era. And it really is and we’re going to show how Harmonic Convergence and her battle with Unalaq and Vaatu kind of shifted the world a bit."source
Grey DeLisle, who voiced Azula in ATLA and the scorpion spirit in the Korra Book 2 finale, will be voicing a "bad girl" in Book 3. This character will NOT be a firebender (and not necessarily evil or a villain). She will also play a waterbender who is now speculated to be this character. source
The giant vines Vaatu created in Republic City are still there and spirits now roam them! source
Book 3 stills:
Book 3 production progress:
All voice acting has likely been completed.
The first four episodes’ “Take 1 animation” has been completed. source
Bryan has confirmed the current reigning monarch of the Earth Kingdom is an Earth Queen. Given that Book 3 is supposed to focus on Lin, many people have interpreted this together as an indication that the Earth Kingdom will be featured and this Earth Queen will appear in Book 3.
Furthermore, production on Book 4 is underway as well.
Book 4 is the confirmed end of the show, with 13 episodes.
Jason Isaacs (Lucius Malfoy - Harry Potter, Zhao - ATLA), Jason Marsden, and Anne Heche have been added to the cast in at least one scene with Jinora. source
There is at least one scene with Katara and Korra. source
Hopefully with the shorter wait for Book 3, we will be getting more and more information soon!
This post will be updated with new information when it becomes available.