According to IGN, the next incarnation of the PSP is on its way. And it's taking a few design cues from the iPhone. (Their words, really!)
IGN has learned from several credible sources that the PSP 2 is indeed on the horizon, and will be packing multi-touch technology. According to our sources, the PSP 2 will feature a widescreen multi-touch interface comparable to that of the iPhone for both in-game control and menu navigation.
The point of the touchscreen controlling in-game features is a big one, signaling that this is not the PSP-4000 we're talking about but a full-fledged PSP2. (Hardware revisions that will wildly affect gameplay are reserved for new platforms.) It's also fairly believable since Sony put the option into a recent customer poll.
Of course, IGN's release dates of "coming soon" and "on the horizon" have widely varied connotations. To me, that could mean "next week" or "next decade."