According to author, the fifth (and, as she stated, possibly last) Theodosia book will be "Theodosia and the Flame of Sekhmet" (working title). The author's estimated release date was sometime in 2012, but with that year now gone, it is unknown when the fifth book will be published. As of August 2016, the author has stated on her blog that no further books in this series are likely to be published: http://rllafevers.blogspot.com/2016/08/at-long-last-update.html