According to the recent leaked information, the PS4 will be using AMD's A10 APU. What is interesting is that how much the chip design resembles to that of smartphones. You are not only getting CPU and GPU on a single dye, but also very very power efficient compared to what is used on current consoles.
Also this unification will also mean the CPU and GPU can work in tandem without sharing a bridge like Xbox 360 does. Which would mean the GPU can times offload complex geometry calculations to the CPU and the CPU similarly can leverage processing power of the GPU when it is not used, example during load times both the CPU and GPU will work together for incredible load times. While a reasonable 8GB SSD can be used for essential system functions and can speed up the system even more.
Good times indeed :)