Thanks to a certain anonymous contributor on the wiki, I've been alerted as to the recent title of the sixth volume in the series. I didn't believe it at first, but when I searched the title, I came up with a result from Amazon. The next installment in the series will be titled Escape From Lucien.
Now as far as titles go, Amazon is our most reliable source. They will often get ahold of such information a few months before the actual release of the book. It's happened with past volumes, and there's definitely no exception here.
Additionally, Amazon lists the release date as August 26, 2014, which makes sense considering Kazu has stated numerous times via Twitter that he expects it to release during Fall. Speaking of which, Kazu also stated recently that the book is in its last month of production.