Supposed images of a "PSP2" prototype (pictured) were leaked in November, followed in December by the detailing of alleged hardware specs. The PSP successor is assumed to be in development alongside the PlayStation Phone, and Sony has already acknowledged the challenge of differentiating two such devices in the consumer market. Coming out and announcing them already would probably be a good start.
Update: Sony has confirmed to Joystiq that the company will hold an event in Tokyo on Jan. 27. "We will be sharing business [overview] and strategy," said a representative, "but there is nothing we can comment on further at this time."