The last major redesign of PlayStation 3 hardware, the release of the PS3 Slim in September 2009, was an enormous success for Sony, and has led to rumours that another redesign, a "PS3 Super Slim", will be announced at some point to try and get a final stretch of mileage out of the system.
The appearance of something called a "12GB SSD PS3" (the SSD presumably referring to a Solid State Drive, considerably more expensive but also far more efficient than a regular HDD) in the store of a Polish retailer gives some evidence to this speculation. There is reportedly also a 500GB version available (presumably without the SSD, as a solid state disk that size would be extremely expensive). This may or may not be a picture of the system:
Polish site Polygamia.pl lists the 12GB as costing €199 ($260) and the 500GB as €299 ($391) - note that the US prices will probably be considerably cheaper than this, if Sony follows the usual trends of selling for higher prices in Europe.
If anything is officially announced, it will probably be at the Tokyo Game Show. Sony's press conference is on Wednesday 19th September at 5am UK time (Midnight EDT, 9pm on the 18th PDT). We will keep you posted if Sony makes an announcement of any kind.