Book of Circus western DVD release speculation
First, I predict it will be a set, bundled with Book of Murder, simply because of how short BOC is, as well as the fact that past BB releases came with their OVAs, so I don't see a reason why that would change now.
Second, I think that if they've held back this long on releasing BOC, it's more than likely they're waiting to A) get BOM sorted with the dubbing and B) probably looking at a fitting release window, so I could see BOC/BOM being released around October for Halloween, given the show's subject matter, or even at Xmas time (not sure what to get for the Otaku in your family for the holidays? BAM, there it is).
Those are just my thoughts. I imagine FUNimation will put out something in the next few months, maybe sometime near or during the summer.