I don't see anything on the Black Library site.
"Hidden Depths" ends with a blatant excuse-to-call-in-Cain cliffhanger, but it's been over a year since that story was published.
I expect that their will be more Ciaphas Cain novels to come but Sandy Mitchell is probably deeply involved - along with The Black Library's other top authors - with the upcoming 40k end times event rumored to start 2016 & may also be writing for the god awful Age of Sigmar reboot of the fantasy line.
I really want to know how the end times plays out.. There's so many possibilities from the star child to the black crusade succeeding to the primarchs coming back., I, genuinely scared for the empire of man.. They are screwed unless the emps comes back