I just posted a blog post addressing this topic. Book six is completed and at the editor's office. She's working as hard as she can, but she's a busy woman. I wasn't able to release earlier because I didn't finish on time. There were some difficulties with the plot that I needed to sort out in the best way. That took some time to figure out. Remember, there's still four more books to go in this series. Certain aspects need to be fit in now to follow through later.
Here's a link to the blog post detailing the release of the print books 1-5. I hope you'll check it out.