Recent rumors have said anywhere from 4.5GB to 7GB of GDDR5 RAM will be available to developers on the PS4. However, we can now say that at least 6GB of RAM will be free for developers to use. Previously, Digital Foundry has released rumors that the PS4 will only utilize 4.5GB. These rumors were recently squashed by PlayStation 4 developer Brian Provinciano via Twitter. Brian is the head of Vblank Entertainment and is the creator of Retro City Rampage.
@mrnray It's absolutely false. Absolutely ridiculous.
— Brian Provinciano (@BriProv) July 27, 2013
Also, a well know insider at NeoGaf by the name of thuway shed some light on how much RAM will be available to developers.
There are games in development that are using 6 GB of RAM. I will not say any more about this.
This means means more RAM will be available and the OS will be less of a resource hog then previously speculated. In addition, more memory means larger draw distance and better textures, which can in turn make the console have a longer life cycle.
So, it appears that the PS4 will in fact have more RAM available to developers than previously rumored. The exact amount isn’t clear but we know now that at least 6GB will be free for developers to utilize.