Hopefully you’ve fallen in love with The Legend of Korra by now because Mike and Bryan reportedly have no intention of ending the series at Book 2.
According to Inside TV, 26 more episodes of The Legend of Korra have been ordered on top of the 26 current episodes. Book 1 includes 12 episodes while Book 2 will include 14 episodes. With 26 additional episodes confirmed, it is unclear how they will be divided.
If Mike and Bryan decide to make Book 3 similar to a season from The Last Airbender, it is likely that all 26 episodes would be devoted to that one book. But if they decide to continue their streak of making filler-less seasons (seasons without filler-episodes), then the 26 ordered episodes will likely be divided into Book 3 and Book 4.
It is currently unclear which path Mike and Bryan will choose (I think they’ll chose the latter) but one thing is for sure: Book 3 of The Legend of Korra is confirmed.