While Sony continues to categorically deny the existence of a PSP 2, at least they're willing to acknowledge the fact that a new iteration of the handheld is not only possible, but probable. Therefore, many sources have been attempting to uncover early rumored details concerning the PSP-4000.
Well, according to VG247 , which claims to have an inside source that has confirmed details and an estimated release date, the PSP-4000 should arrive in December of this year. It will also boast the much-rumored sliding front-screen (pictured over at the site; follow the previous link), and the inside source calls the PSP-4000 a "complete aesthetic overhaul." They expect it to be announced at either GDC or E3 this year, but not surprisingly, Sony refuses to confirm or deny anything regarding a new version of their portable unit. At this point, one can almost expect a new PSP every year, and each time a fresh entry arrives, Sony sees a sales spike for the handheld. Of course, they could always generate more spikes by releasing awesome software between now and then, but it's no secret that sleek new gadgets always appeal to the North American masses. Hopefully, Sony will make the PSP-4000 announcement at some point, so we can at least report on something besides rumor and "inside sources."
As for the PSP 2, that idea remains clouded in shadow. One recent update is that Sony may be testing for a new piece of hardware, and that it has connectivity with the PlayStation 3, but that's hardly enough evidence. We'll keep you posted, though.