Hey guys don't you this Yoshida this statement is like a joke?
From sonyps4playstation.com/ps4-development-has-been-running-since-2006/: "According to Shuhei Yoshida, president of Sony’s Worldwide Studios, the Japanese manufacturer the working on ps4 development since 2006.
In an interview with the game magazine Edge, he explained that already shortly after the PS3 had employed a small team of engineers with the design of the successor console in November 2006-relase.
From 2008, the Yoshida further, then a larger group of employees have in parallel with the development of the PS4 and Playstation Vita busy. The aim of the cooperation is to ensure the optimal fit for both game consoles. Here we have focused mainly on the cross-controller and streaming functionality, Said by the Sony manager."
I don't believe Yoshida said true, just for media attraction, bcz its sure sony also don't make final about its hardware before 2013.
IMHO his statement seems to be plausible. According to Wikipedia development began in 2008. However it was clear even before PS3 was finally released that lot of studios complained about the CellBE/PPC architecture which required from the scratch development of the game engines.
So after release of PS3 in 2005 and be aware that CellBE will not improve largely in price, speed and lower power consumption the devs in 2006 started to estimate the base architecture for the successor. So there was not a lot left to choose other than ARM, MIPS or X86.
Probably they had a close eye to these and evaluated the platform including possible vendors etc. from 2006 to 2008 where they finally decided to switch to X86.