Hey you posted that a while ago but I was passing by and your comment seemed lonely...
The author said there will be a 4th and final volume to this story. Not sure about publication dates though ! The books are published in French, those chapters are up to date to what's been published, but the 4th volume has been announced a few months ago, without any more details, so it probably should take a few more months to have some news :) (probably october/november)
Has it been discontinued? :(