Sounds like they are going to be giving book 3 away. Brandon Sanderson confirmed this in his weekly update video.
Bands of Mourning will be the September book of the month, available from Sept 13 through Sept 16. News is from Brandon Sanderson's Weekly Update:
https://www.youtube.com/watch?A9yc_6eQeNI starting at 2:15. Sign-up and get your link tomorrow.