Sony will most likely use the Existing Cell Processor that is housed within the PS3 up until the Playstation 5 as it can be upgraded Significantly.
The PS3's Cell Processor has 8 Single Cores which run at 3.2GHz each! 6 are for gaming, 1 is for the PS3's OS and Security Features and 1 is not used at all! No reason has ever been given to why 1 Core has been disabled but Developers have said that it would have come in handy!
The PS4 has been Rumored to be 10X More Powerful than the PS3! Utilizing the Cell Processor and making it Dual Core, 2GB of DDR3 RAM with a GDDR3 GFX Card possibly being 512mb dedicated and by using Holographic Disc Technology it would allow Terrabytes of Data to be stored on a Gaming Disc instead of Gigabytes! (Holographic Disc Technology has already been able to produce a Disc that holds about 3 OR 4 Terrabytes worth of data)