Eurogamer's "close to Sony" source is to be believed, these are the changes you can expect to see in the next iteration of portable PlayStation. The screen is supposedly the same as the PSP-3000, with the only difference being that it can slide. When in the "closed" position, the unit will be "significantly smaller in width" and most controls will be inaccessible; however, shoulder button-only games like LocoRoco will be playable while in this state.
The noted hardware change, which would make the PSP a UMD-less device, mimics statements made by former COO of Acclaim Dave Perry last week -- to which Sony's PSP marketing head John Koller offered a vague non-denial. With the PSP-4000 rumored to arrive later this year, it won't be long before we get more verifiable information.