Does anyone know if there is going to be an actual criminal investigation into this?
If Fish files a complaint, there will be a record of an investigation somewhere, but who knows how thorough that will be. Valve's hacker only got caught because Valve did their own police work on it, and Valve is many times larger than Polytron.
Imagine you're a cop and you get this case. Your suspects are people on twitter and 4chan, there's no theft of assets, only a defaced webpage with personal data, a picture of the five guys logo, and a .zip file with a bunch of documents on "Fez" sales from "PlayStation+."
Not exactly bank robbery, shots fired.
The FBI would need to get involved and I don't know if they have the resources or inclination.