Given that Philly created a detective story and then a cyberpunk, it's very possible he may try yet another genre and continue to avoid repeating himself.
There are plenty of stories out there which could still have the Philly atmospherics without being an echo of anything he's done before. I'm personally rooting for something sci-fi (like really in space, not just the future) with Philly's brand of gritty realism.
I know he's also shown some interest in Lovecraftian themes...that would be amazing.