Edit: 1/24/2015
New Evidence: Confirming it's a fake.
The dimensions of the PlayStation 4, as mentioned in the official specification sheet released by Sony, is 275×53×305 mm. This means that the PS4 has a width of 275mm. The size of a standard Blu Ray disc that the PlayStation 4 uses is 120mm. With those numbers in mind, a Reddit user estimated the width of the alleged PlayStation 4 Slim.
As shown in the image below, the user estimates that it comes out to be 166mm. The size of the Blu Ray player comes out to be 84.17mm, which means there is no way that a standard Blu ray disc will fit in this design. Now there are smaller sized discs available (80mm) but they are capable of holding only 15.6GB. In short, the alleged PS4 slim won’t have a big enough Blu Ray drive to accept games disc. This proves that the design is nothing but fake with ridiculous dimensions concept.
Original Story
There have been many reports/speculation on the internet about PlayStation 4 Slim already being in development at Sony, and an official announcement might happen at E3 2015 or at GamesCom 2015. Today, on Multiplayer's Italy website, the first image of "PlayStation 4 Slim" was leaked, according to the details in the image, PS4 Slim might be internally code named as "Monolith".
Gamepure
For comparison here is the PS3 to PS3 slim: Everyone thought the leaks were fake and they turned out to be true.
For comparison here is the PS2 to PS2 slim
Source: http://www.vg247.it/2015/01/22/ecco-la-prima-immagine-di-playstation-4-slim-oppure-no/
English Source: http://www.gamepur.com/news/17745-first-actual-image-ps4-slim-model-leaked-pretty-small-size-compared-current.html
Edit: Special thanks to BraLoD for the correction, new news has arrived that logically concludes this Slim is a fake.
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