Sony is not going to have a 2nd GPU. There have been no rumors to suggest this either. Just people speculating because they didn't like the APU performance.

http://www.ps3news.com/playstation-3-psn-news/rumor-playstation-4-ps4-orbis-processing-specs-uncovered/

IGN for original rumour (Too lazy to find it on IGN)

"APU will work in tandem with the system's dedicated GPU, the HD 7670, a DirectX 11-enabled card clocked to 1GHz with up to 1GB of dedicated VRAM."

I'm a bit surprised you missed these rumours.

I expect at least a better APU than A10-5800K... 512 cores @ 800MHz.

IGN is IGN nothing more. (that rumor also has 2GBs ram and it at one time believed the immediately dubunked ps4 spec sheet)

When you read these rumors from the beginning (not your link but since I've been running this thread) you see that it started as an A8 then moved to an A10. Rampant speculation has always been if the A10 would be based off current 6xxxx gpu or using a newer 2013 APU with the 7xxxx gpu.

I have never seen credible rumors that show it as having a APU plus a secondary GPU. I only added the comments to such in the OP to appease various posters who pushed that idea.

I trully think it will be a A10 based on current teck with teh 6xxx gpu base as the current on the shelf A10s do. Sure it will be tweaked and such, but no 2nd GPU. (similar end result with Xbox)

Then expect to be dissapointed I guess.

It will be based on the current A10, then of course tweaked for Sony's specifications... for better or worse.

No rumour is credible though...  Most signs point to an APU and more of the earlier rumours pointed to an APU + GPU.  Just cause no recent rumours mention a dedicated GPU doesn't mean it's not there.  Same with the new Xbox, rumour started out with an array of ARM processors, turned into an oct core PowerPC, then went to an FX processor, now going with some custom APU, I wouldn't trust any of those sources.  PS4's specs have mostly started with APU + GPU combo, all rumours since have been stating the APU is slowly getting upgraded (Most likely due to newer dev kits), they've just never mentioned anything of the dedicated GPU since as it's probably not changed since the first rumours.

as far as I know only one rumour doesn't mention a second GPU. And that rumour also states they are targeting 1080p60fps for games, and even with current gen levels of detail would need a GPU at least 4-5 times as powerful as the one in the A10. So that rumour it's self is ether invalid or also suggets that there will be a very powerful GPU to back it up.

http://translate.google.nl/translate?sl=auto&tl=en&js=n&prev=_t&hl=nl&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.psx-sense.nl%2F89207%2Fexclusief-talloze-informatie-over-de-playstation-4-inclusief-specificaties%2F

1.8Gflop codename Tahiti 

seccondary source, most likely repost

http://www.vgleaks.com/world-exclusive-ps4-in-deep-first-specs/

Also 

"The right time to talk about new advances in hardware is when you can demonstrate a significant leap on the current experience, and something that is going to be attractive."

http://www.computerandvideogames.com/354391/sony-we-wont-show-ps4-until-it-can-demonstrate-a-significant-leap/

A stock A10 is not a significant leap in hardware. 

And also some interesting Crytek stuff

"We were one of the first studios in the world to get access to all of the next-generation consoles. Obviously we can't talk about what they are but we know what next-gen entails. I think people... I'm not going to judge it because it'll get me in trouble, but next-gen is actually not a clear picture right now."

http://www.computerandvideogames.com/352932/crytek-were-already-way-beyond-next-gen-consoles/

"If they find ways to cheapen the cost to a degree they could triple or quadruple their memory. Just say, 'Hey we're going to have 32 gigs of memory.' That would be quite amazing because memory can do so many more techniques and tricks."

Suggests current next gen spcs have ~8GB if 4x is 32GB

 "That was our guess already two years ago. That's why we said back then that 'Crysis 3' is next-gen ready already. We did that without knowing the specs, but it's not going to be much more than what we have done so far. And it turns out we were pretty much right. But the focus of next-gen is in a different area.."

suggests that next gen is capable of running Crysis 3 and maybe a bit more.

"The current generation consoles, when they launched, were far ahead compared to PC. But PC has caught up. With current generation consoles and what's on the horizon -- new ones -- due to the fact that the cost of CPU and memory are so much more expensive than they were in the past, it is simply impossible to have the same kind of impact on the console business; to be so far ahead of PC,"

Obvious that next gen won't be much better than current high end PC, or better at all for that matter. But the wording is interesting I guess the reason he doesn't say it won't be close to current high end PC is probably NDA but could mean that next gen will be closer to high end PC today than some may think, also confims in a round about way that next gen is off the shelf stuff. 

Not to mention Crytek basically just confirmed today that next gen consoles could easily run Crysis 3 on max settings.  He said they "aimed for Crysis 3 to look next gen and now that theyve seen the new consoles they got close"

So we know the coming systems are powerful and as far as I know an A10 cant run Crysis 3 at High settings

The problem is that the guy contradicts himself. He also said, "CryEngine tech is way beyond next-gen consoles already". And when you take into account this paragraph:

"Yerli's comments suggest that he and his team know all about the capabilities of Microsoft and Sony's next-generation systems. But what exactly is he prepared to let on? Well, for starters, he thinks that the current high cost of memory and processors means that it's "impossible" for next-gen consoles to make an impact similar to that of the previous generation, and as a result, "the focus of next-gen" is not on graphical horsepower..."

... it sounds more like the next-gen consoles will fall a bit short of what some people are expecting.

Reposting this, some might find it interesting. As you can see from the table, 7660D inside A10 is only some 2x as powerfull as Xenos - releasing next-gen console with only that kind of improvement honestly doesn't make any sense. If Sony really decided to go the mid-road approach, A10+6670/7670 would be probably best bet - that would pretty much be in line with that PS4 = 2-3x WiiU, and NextBox = 2-3x PS4 rumour.

EDIT: Of course, that APU inside PS4 might end up being fully HSA capable, and not used for graphics at all, having PS4 relying on separate GPU for that tasks.