There is leaked info about Sony releasing an updated version of their PSP next Spring. The biggest difference if the 8GB of built-in memory. Expected update everything and maybe even a smaller footprint, but for now nothing is for sure yet.
One bad news is that it looks like the PSP will be holding onto the UMD format for their disks. There are also talks of a hard-drive PSP will cost more than the flash memory of course.
My guess is that they will add in a camera and WiFi capabilities too, but who knows.