While it is unrealistic to assume that Sony will announce a new PSP anytime soon, considering that the PSP Slim (PSP-2000) is still relatively new, more evidence that suggests a third-gen PSP is in the works has surfaced.
Poking around on the online PSP manual, one individual found a 65x13 GIF format image that denotes the text "PSP-3000." The site contains similar labels for the PSP-1000 and PSP-2000 series. Is it just a creative mock-up or a logo that Sony is planning to use in the near future? Hmm.
The discovery follows reports from homebrew developer Mathieulh, who found a firmware file relating to a possible third PSP hardware revision back in December of last year.
Online PSP Manual [Sony via PSP Fanboy]