A recent filing for a PSP related patent turned up with Sony’s name, and involves an idea to dock controllers to the PSP. The idea is that a controller would be made dockable onto the PSP using some kind of “control docking apparatus”. This would prove beneficial to gamers since it would could mean an extra analogue stick or even rumble if the PS2 controller could be docked.
The SIXAXIS could also play a part in the new device, since the patent mentions that “the electrical interface can be a wired or wireless communication link”. You can check out the patent application here.