it doesn't say specifically if the book will or not. As it's still in the process of being written, it's up to the author and editorial staff to decide what the book is going to cover.
You can however contact the author directly on his website:
He may be able to give you a better Idea as to what the book is going to cover.
Customer Service Rep,
I'd love to do a single chapter on Go in the 2nd edition, but unfortunately it's a low priority compared to many other features they've released since the 1st edition came out, and we have an aggressive writing schedule. If I do have time, it'll probably take the form of a single tutorial chapter, and not be spread across the book like Python and Java are.
Thanks for your interest!
Author, Programming Google App Engine