According to Gamespot's translation of a job posting on the official Sony site in Japan, the company is looking for an "evaluator/assessor" for a "new game machine." That is "part of the PlayStation or PSP series and their peripherals."
Should you get the job, you will be "part of an advisory staff which will play PlayStation series software on this new machine and check its functionality," and "test game machines not yet released or new functionality of PS3 peripherals before they are released."
What is this mystery Sony machine that needs testing? Perhaps a new iteration of the PlayStation Portable? Maybe some sort of PS3 peripherals? Or could it be The PlayStation 4?? Okay, that last one is very doubtful, but no one knows for sure...so it could be.
Sony said it's preparing a response, so hopefully we'll know more soon!