This time, an insider at PocketGamer claims that PSP2 or PSP-4000 will be out in stores just in time for Christmas. He says that it will have a compact design, big touchscreen, slide mechanism, and dual-joysticks. Seems like it wont use UMD either.
To me, this sounds like yet another rumor. We've all heard about people wanting touchscreen, dual analogs and slide mechanism. And seen the million pictures around the web of possible next gen PSPs. Not to mention all the people saying that touchscreen would be too much like DS and slide would be like a smartphone.
If any of this is true, it will probably be proved in a near future.
But like with the PSP-3000, hopes were great and dreams were crushed. So don't get your hopes up.