The author had written in the afterword that there still will be a book with short stories that will be released after this and that she has her next series already thought up (I don't know if she has started to write it though.)
I also purchased the Cobalt Magazine 2013 May issue which is a special edition that celebrates this Hakushaku to Yousei ending after 9 years. It has a short story written in it and a little book dedicated in HakuYousei with a timeline, anime voice actors questionnaire, a message from the manga artist Ayuko and many other little things in memory of Lydia and Edgar. And I will translate that when I reach translating the last book, so please rest assured.
Till then, I'm working on the next chapter.