If that Neogaf post is true, and frankly it smacks a bit wild/out there for my tastes, then we really are down the rabbit hole. No way Microsoft couldn't respond...
2X GPU, at least 3.6 TF, I dont keep up so much with desktop GPU but that's still pretty dang beefy/power hungry I'd think. Dont know, keeping my salt handy...
This is pure speculation but if you are trying to look for an equivalent desktop gpu we are looking at something around a R9 380.
Heres why:
PS4 gpu compares to a HD 7850
HD 7850
Released: 1.5 years before PS4
Clock: 860MHz
Teraflops: 1.7
Max TDP: 130
Cost: $250
R9 380
Released : June 2015 (1.5 years before presumable PS4.5 launch)
Clock: 970MHz
Teraflops: 3.4
Max TDP: 190
Cost: $200
But who knows what Sony and AMD are doing.