So we found out a few weeks ago that Studio Mir were doing part of Book 2 along with Pierrot Co. Just recently
Studio Mir on facebook confirmed that they will be animating all of Book 3 themselves and I would assume that they will do all of Book 4 also.
It does really make me interested in the exact details of why Pierrot Co were brought on board and not kept for the remaining books even just to do an episode or two. I think this more or less confirms why Book 2 has take so long, Pierrot Co had to be brought up to speed and Mir must have only come on for Book 2 later. We have a few conflicting reports over the exact details of Pierrot Co's involvement, but we will find out as Book 2 airs. I am wondering just how many episodes they animated, so far we know they are doing K201 Rebel Spirits, and that Mir say they have worked on half of Book 2. So I would lean towards K201-K207 being done by Pierrot and K208-k214 By Mir.
From what I have seen of K201 the difference in animation is nothing too big, the styles match better than ATLA's multiple studios. I guess Mir just want to make sure there is zero drop in quality that could impact their reputation and so decided to do the rest themselves.
