Well... It's really hard to believe the AMD make a custom GPU for Sony when they need to spent less money than the others... if that is not GCN2 then it's a GNC enhancement with features to come in GCN2 (a preview).

There is a thread about PS4 GPU based in GCN 2.0.

http://www.neogaf.com/forum/showthread.php?t=515746

@Chark

About the Durango changes I found that.

http://www.neogaf.com/forum/showpost.php?p=48272238&postcount=211

"Specs for Durango haven't changed. The GPU is nearly 100% efficient though at 1.23 TF, so that's something most people didn't know." 

So if it is 8xxx, which I find odd because I think even Yoshida was talking 7850 in an interview I translated.

"GPU core architecture "Graphics Core Next" new generation of AMD (hereinafter, GCN) GPU core that has been found to be employed. I used to adopt an architecture called "Jaguar" CPU core (or Jaguar Jaguar), for here will be described later.

Well, GCN, the architecture that is employed but has been known GPU series codenamed "Southern Islands" as development (Southern Island), the Radeon HD 7000. Sony Computer Entertainment Inc. (hereinafter, SCE), which has been APU of PS4 is equipped with a "compute unit of the group 18", in the GCN, the compute unit "GCN Compute Unit" is a scalar floating-point processor 32bit (= Shader because the core) "Stream Processor" (hereinafter, four pairs are contained as a set group of 16 SP), the entire APU of PS4, will be equipped with a SP of group 16 × 4 × 18 = 1152.
Belongs to the 7800 series Radeon HD "Radeon HD 7850" number of 1152 based on this, it is calculated that the middle "Radeon HD 7870 GHz Edition" and the group (1024) group (1280).

4 PlayStation body and block diagram overview of the Radeon HD 7800 Series

In addition, there is the spec was released, and has the processing performance of 1.84 TFLOPS, assumption that group 1152 Number of SP, in the GCN architecture is the fact that SP that can perform (2 Ops) summing the product one on one clock Given, from the formula of "(1.84 TFLOPS ÷ 2) ÷ 1152", also derivable operation clock of about 800MHz. Close to the same Radeon HD 7870 GHz Edition 1000MHz and 860MHz rated for Radeon HD 7850, It's a number with a sense of reality."

Where did you get that?

Yoshida said there is changes in PS4 hardware to be show yet.

Also this, if it adds anything.

"In addition, the information has been written in the official specification was published, the bandwidth of GDDR5 memory bus that is 176GB / s, you can also guess memory performance. So 256bit, memory interface of the Radeon HD 7800 Series "per" would be 256bit graphics memory is also given in the APU interface of PS4 probably, if it was temporarily 128bit, is too high data rate per 1bit. If the 256bit that point, you will be asked "176GB / s ÷ (256 ÷ 8) = 5.5Gbps" called plausible values, with the 256bit interface data rate of 5.5Gbps (5.5GHz clock operation) would be correct .
So 4.8Gbps, the data rate of graphics memory and the Radeon HD 7870 GHz Edition Radeon HD 7850 has the impression that this point is a little luck the way the PS4."

http://www.4gamer.net/games/990/G999024/20130224001/

He tweeted it, I think it is an interview with him.

It's like a FAQ... the site created the questions and answered them... not Yosh relaed.

Just to add true data for my GCN 2.0 theory.

The Sea Inlands ISA Manual (GCN2): http://developer.amd.com/wordpress/media/2013/02/AMD_Sea_Islands_Instruction_Set_Architecture.pdf

Important differences between S.I. and C.I. GPUs

•Multi queue compute * EIGHT queues and EIGHT ACEs is what the PS4 GPU have *
Lets multiple user-level queues of compute workloads be bound to the device and processed simultaneous. Hardware supports up to eight compute pipelines with up to eight queues bound to each pipeline.
•System unified addressing * That's the HSA present in PS4 GPU to share memory with CPU *
Allows GPU access to process coherent address space.
•Device unified addressing * Again. That's the HSA present in PS4 GPU to share memory with CPU *
Lets a kernel view LDS and video memory as a single addressable memory. It also adds shader instructions, which provide access to “flat” memory space.
•Memory address watch * I don't know if PS4 GPU have that *
Lets a shader determine if a region of memory has been accessed.
•Conditional debug * PS4 GPU don't need that... that's for debbugers *
Adds the ability to execute or skip a section of code based on state bits under control of debugger software. This feature adds two bits of state to each wavefront; these bits are initialized by the state register values set by the debugger, and they can be used in conditional branch instructions to skip or execute debug-only code in the kernel.
•Support for unaligned memory accesses * I don't know if PS4 GPU have that *
•Detection and reporting of violations in memory accesses * I don't know if PS4 GPU have that *

My comments in BLUE. 

So even if it isn't a full GNC 2.0 sea islands 8xxx series, it might as well be.