There has been an overwhelming amount of rumors surrounding the new PSP model and what would be included or excluded this time around. 1UP.com has "confirmed" many of these rumors, but be warned; 1UP.com states these facts are being confirmed by their "source", until an official statement is released from Sony these are still to be taken as just a rumor.

According to 1UP's "source" the new PSP is to be called the PSP Go! and will be released this October or November in America. It's also said that the new PSP will be released in two different SKUS, with either eight or 16 GB of built-in flash memory and there will be over 100 classic and new PSP titles available for download the day of launch. As far as hardware, 1UP is stating that their source has confirmed "a d-pad, analog nub, and face buttons as part of a sliding unit sticking out below the screen."
All this sounds really interesting and quite promising, but for now, it is all still speculation and rumor. It is said that Sony will announce this among other things about the new PSP at this year's E3 in June.
Source: 1UP.com - "New PSP Named And Coming This Fall"