I don't think this'll be a follow up from Punchline Chapter 15, the cover is probably a fake out, or a homage to/inspired by Catwoman 51.
Yeah between the prison video and the Bluebird video I wouldn't be surprised if Harper and Cullen are on the run right now, in one of Batman's safehouses. I really was hoping Harper would make an appearance in this series but from the solicits it seems like Punchline is going for as much notoriety as fast as possible. This is going to bite the Royal Flush Gang back hard.