Seems a little "on the nose" for a Blackstaff focused book, maybe? Almost like calling the final novel "Last Book", or if skin game had been "Godly Heist" 
I think Im swinging back to the last book being "Well F*ck", with the plot centering around two inmates in Demonreach getting together and spawning some world-ender offspring 
My reason for "Dark Pact" for the Blackstaff book is that I think that whomever takes up the Blackstaff makes a pact with someone, or something. Also there could be a reason Harry has to take up the staff similarly to taking up the Winter Knight mantle.
I don't think Jim, or the publisher would use a book title with profanity.
Another possible book title:
Long Shot
why? Well he uses the handle Longshotauthor, and I think he uses the handle long shot when he plays video games sometimes.
