A recent FCC filing from Sony has outed a new hardware model for the PS3. The documents compare the size and registration label position on the original "fat" 2000-series console, the current "slim" 3000-series model, and the upcoming 4000-series, a.k.a. the "super slim" PS3.
The biggest change in transition from the 2000 series to the 3000 series was new, energy-saving version of the console's Cell processor. The hardware was also smaller and lighter, obviously. Based on the diagrams, the new console will clearly be smaller, but there's no word on any new technical changes inside the box. However, Sony did file a pair of debugging stations - DECH-4001x and DECH-S4001x - implying that there are new chips present in the console.
Rumor has it we'll be seeing the PS3 Super Slim sooner rather than later. Sony may unveil the hardware update at Gamescom next month, according to Eurogamer.