Yonezawa just announced on Twitter that he’s planning on releasing the newest Hyouka volume in November this year. The release will include all of the previously unanthologized short stories up to this point (4 of them so far) and will contain new material as well, which he will expand on at a later date. I’ll be translating this as soon as it comes out, of course!
He also announced a new short story for his Petit Bourgeois series, which he states will not be a part of the 4th and concluding volume, but hopefully will bode well for its eventual release. This is his second biggest series, next to the Classics Club Series, and fans have been waiting a couple years short of a decade for for the last volume.