gamescom reveal could be imminent

Sony is currently working on a 4000 Series PlayStation 3.

What does this exactly mean? It seems the company is preparing to launch a slimmer model of the, well, slim PlayStation 3. The current PS3 model is the 3000 Series, with the model referred to in the filing being the CECH-4001x.

Adding further credence to a super slim PlayStation 3 being readied, an image was included in the filing that compares the 4000's model to the 3000's model, with the latter's size being considerably smaller.