The RAM in modern gaming PCs is already equal or higher than 8GB, which is shared between the CPU/GPU on the PS4. The difference is that it's DDR3 RAM, whereas the PS4's is GDDR5. In the future, it's possible that there will be PC motherboards that support DDR5 RAM as system memory, but it's not happening at the moment.
Of course, when talking about raw computational power, as @
Wajhi said, it is already greater on PC hardware of today, let alone tomorrow. One can't expect a $400 machine to match a PC, where the GPU alone can potentially cost the same or over twice as much.