Compile Heart has opened up the countdown site it teased in this week's Dengeki PlayStation. The site appears to be for a new game that has the codename "NPG."
The text to the upper right says something along the lines of: "That system will tremble in your hand like a little girl."
With what appears to be a video game system theme, there's some speculation that this may be a sequel to Neptune with a focus on portable systems rather than consoles (fitting in with that heap of consoles to the left).
We'll apparently find the true identity of NPG in 500 or so hours.