Eurogamer, numerous publishing sources have confirmed that Sony is at work at a third hardware revision and it's planned to come out next year. Not only that, but software developers are reportedly busy working on games for a "PSP2." There were no specific details revealed involving either hardware. The PSP2, unlike the PSP-4000, has not been given any sort of timeframe.
Despite how assured Eurogamer is on the credibility of the information, Sony continues to give the usual "won't comment on rumors and speculation" response. In fact, it was not too long ago that SCEE head David Reeves denied the existence of a PSP successor as rumors unfurled from a tech deal.