Sony has redesigned their consoles in the past for various reasons; some aesthetic and others for hardware improvements. In the case of the PS3 redesign, it was for both. But it seems that they aren't done fiddling around the PS3. So instead of focusing all their hardware energy on the PS4, it looks like they are producing another PS3 model.
They filed paperwork with the FCC for a new model code CECH-4001X specifically for the PlayStation 3. They are currently on the 3000 series.
That's all we know for sure, as Sony has not officially announced what new capabilities the system may have, assuming that it has any at all.