As said a million times before, quad core support will be VERY hard to implement and will give a relatively small speed boost.
Comparing the speed boost of using 4 cores instead of 2,to 2 cores instead of 1 as creamsoda did is totally wrong.You must also consider the HUGE overhead of keeping everything in sync,which could finally make it SLOWER than faster.The sync issue could also cause many compatibility problems / crashes so quad core support is not something to get that excited about.
Although there is a possibility it will be implemented and work relatively well,it will not be something as groundbreaking as MTGS was when it was first put in PCSX2