According to the japanese version of Amazon, Overlord volume 10 is to be released in 2016, 05, 30 meaning the 30th of april.

I found this by looking at the wiki for overlord, the novel (Which i might have done abit too much lately..) and thought you might be interested if you are reading it. Do have a look at the wiki and just incase you won't, i shall say that the aurors blog mentioned that the dwarves arc of overlord will be moved to the 11th volume, or so i read.

I thought you might want to know 🙂

Morraren.