"Release dates for this book are still in flux. Even if I finish it early next year, it could be a year or more until you see the book. The amount of editing, continuity, and art that these books require creates a need for a long lead time. I’ve told people that Fall 2016 is the earliest they’d see it, but my team has been warning me that’s not realistic. We’ll see, but for now you should assume on a 2017 release."

http://brandonsanderson.com/state-of-the-sanderson-2015/