What started this whole ball rolling were a series of leaked, low quality photographs depicting molds and packaging art for a slimline PS3, taken in a Chinese factory. The photographs were originally posted on a popular Chinese message board, and subsequently spread to numerous gaming sites across the world. The molds were professional looking and the packaging was not photoshopped, indicating either that the pictures were legit or that someone went through a great deal of effort to fool the internet.
China is notorious for producing imitations, and game consoles are as much a victim to this trend as everything else. The Chinese market has seen dozens of console knock-offs already, the Vii and PolyStation 3 are two such examples of this. However, this particular PS3 model has the official Sony brand name on it. Though the typical imitators come close in appearance, they never go as far as to actually use the official, copyrighted brand names. In addition to that, the design is significantly different from the existing PS3 model, where as other imitation models are just miniature carbon copies of the original.
It has also been confirmed that this particular manufacturer, MainTek Computer, does indeed produce and supply PS3s for Sony America. The design of the unique pink/green work stations seen in the leaked photos are similar to the ones used inside the MainTek Computer factory, confirming the location. Further, a comment was posted by a MainTek employee on the Japanese gaming site that first published the pictures, saying “We would like to ask you kindly remove the following pages of your pages on your website because the page contains MainTeK Computer Incorporation confidential document and photos, which were illegally released and posted on your website". The original topic that was posted on the Chinese message board has also since been pulled, under a cease and desist from MainTek. MainTek's interest in keeping these pictures from becoming wide spread signifies these pictures may be legitimate.
This wouldn't be the first time leaks from a Chinese factory have confirmed a redesign, either. Around late summer last year, the PSP-3000 redesign was leaked under similar circumstances. We've also seen other redesigned products, like iPhones and MacBooks, leaked in a similar fashion as well.
Now whether or not these pictures are real, it's certainly possible that Sony could make a slimmer PS3. The internals of the PS3 have shrunk considerably since it was launched in 2006, yet the console largely remains the same size. Sony has shrunk the PS3's motherboard 20-30% with the removal of backwards compatibility. The flash card readers have been removed. Technology has improved – just check out the size of the PS3's current Blu Ray drive compared to the ones Sony is churning out now. Obviously there is some room to slim down the current PS3.
*PS3 Slim concept art by NeoGAF member Goldrusher.