I've noticed that Kai has put together a blog just like this on too. :) And now that the KR series has started up again, I'll give some of my input on how the series will go as well. ;)
The story's evolution, for starters, will really take off after the first half of Book 2. The light, silly tales of Team Rebel in Kein Forest will be replaced by a very action filled second half. Book 3, as Kai as said, will be MUCH darker than its predecessor. It will contain much more violence, sorrow, emotion, and it will be much more graphic, especially in Chapter 47, which will be the darkest chapter in the entire series. The basis of the story in Season 3 will also be different than expected. The series will take a massive turn during Chapters 10 and 11, in which the second big battle of the series will occur.
The characters will go through a great deal of evolution themselves. SLIGHT SPOILERS - You'll be seeing Mina becoming more and more skilled with archery, Chen will learn Earthbending from ____ (even though its pretty obvious), Mitsuki will actually show emotion (but not before hitting Team Rebel where it hurts), and Giu will give up women...jk, and Kama will have her time to shine. And much more!
For Book 2, as Kai stated, we will have two guest writers, Flash and Avatar! Flash is planned to write Chapter 14, while Avatar is planned to write Chapter 15. This will likely bring about some very interesting Chapters. In fact, one of these users, Flash, has already guest writing three chapters so far, which means he has written over one tenth of the series' chapters so far (which me and Kai are very grateful for)! :)
Kai and I will also try to have Chapter 8 and 9 out ASAP. ;)