Sony and Nvidia have been friends for quite some time. While AMD provides the graphics technology behind the Xbox 360 and the Wii, the PLAYSTATION 3 is powered by Nvidia. Considering their partnership, Sony fanboys pay close attention to new moves that Nvidia makes. It appears that a recent job listing calls for a senior eDRAM design engineer, which is used extensively in video game consoles (including the PSP). The chances of a new eDRAM product to be used in a PC is slim, increasing the likelihood that a new video game product from Nvidia is nigh.
Considering Nvidia's exclusive relationship with Sony, any new video game product coming from the studio will most likely be an extension of the PlayStation brand. Considering how the PLAYSTATION 3 just came out, it seems unlikely that they're actively designing the PS4. Is a redesigned PSP, or a successor to the PSP, in the works? ps3gamer14 from the 1UP boards makes a good argument for it, but until we get more concrete evidence, this is simply speculation, at best.