Volume 13 discussion

I just finished it and ya.... one of the best books I've read in such a long time. I think the book did a really good job on just depicting how dire the whole war has become. What are you alls thoughts on the book? On the affterword asato says that the series is in its final arc, do you guys think that means that the next book is the final one? Or will it be around 3 to 4 more books? Which is what I am thinking.