You realize even the latest Vishera FX8350 system (without the GPU) uses as much power as the entire PS3/360?

http://www.xbitlabs.com/articles/cpu/display/amd-fx-8350_8.html#sect0

If you add a dedicated GPU, your console will be using 250-300W of power easily. Good luck cooling that! RROD #2. 

Also, most games don't scale beyond 4 threads. In practice this means that A10-5800K (or FX-4170) is barely slower than FX8150/8350 8-core chips:

4-core A10-5800K = 100%

8-core FX8150 = 103%

4-core FX4170 = 105%

8-core FX8350 = 117%

http://www.computerbase.de/artikel/prozessoren/2012/test-amd-fx-8350-vishera/6/

A10-5800K is just 3% slower on average in games vs. FX8150 but costs far less and uses 77W less power. FX8150 is a workstation/multi-tasking not a gaming processor. 

Therefore, it wouldn't make sense to waste extra $$$ and increase power consumption by 77W by going with an FX8xxx series. If they needed more cores for Kinect 2, they could use an ARM-based CPUs specifically for Kinect 2. These CPUs are powerful enough for such basic video/camera tasks and are very cheap at $20 a pop in smartphones. They barely use any power as well. This way the CPU + GPU would be dedicated to games, but ARM processors would be dedicated to Kinect. No need to share CPU resources for Kinect for the main processor.

The alternative is an evolution of the PowerPC design. For instance, they could use a 4-core 4 threaded Power 7+ architecture. 

You have the option of 4, 6, or 8 cores with each core having 4 SMT (4 threads per core) capability. The lowest IBM Power 7+ CPU would then be capable of 16 threads. This fixes many of the flaws of the Cell and Xbox 360 CPU by being an Out-of-Order CPU architecture. 

PS3 Cell CPU has a peak floating point rate of 12.8 Gflops for each SPE. 

Power 7+ has nearly 3x that per each core, or 33.12 Gflops. The difference is the SPEs in PS3 were largely underutilized, which means it could never hit the theoretical peaks. By having a 4 core / 4 SMT Power 7+, and out of order CPU architecture, this newer IBM CPU design would be vastly superior.

It could go either way, AMD or IBM CPUs would both work. 

You cannot cross-fire HD7770 with A10 APU since A10 has HD7660D which is based on 384 VLIW-4 Cayman architecture. You can only crossfire HD7660D with HD6570 or HD6670. The peak performance of such solution would only roughly equal HD6770 when Crossfire works perfectly. HD6770 level of performance is not sufficient for next generation games at 1080P with Anti-aliasing and DX11, tessellation, etc. Such a system would struggle to run UE4 I bet. 

Yep, in fact, rather than Sony following MS, or the opposite, I was imagining instead devs pushing Sony basing themselves on what they already knew,  under NDA, about MS, so not revealing why, but following their own interest anyway.
AMD boasting could have persuaded devs, and MS too, that isn't a CPU maker, but I have some doubts it could also persuade Sony, that actually has experience in that field and co-developed Cell with IBM. Without further pressure from devs towards x64, but just their hate for SPEs, the most sensible choice for Sony would have been dropping SPEs and switching to plain and simple multicore Power.
BTW, I always used AMD CPUs, I like them and I wish it the best luck, but as good as they can be all x64 CPUs suffer from the original sin of having to waste resources for Wintel BC.

Why would I want to see micro-stuttering XFire graphics? A separate HD7770 has about 6 times the performance of PS3/360 GPU. Good enough for 1080P/60Hz. Use the APU's GPU for more important stuff (like Physics, Move, etc...)

Why would I use Vishivashi stuff?  For example, the stock A10-5700 has a TDP of 65W http://www.techpowerup.com/reviews/AMD/FM2_APU_Review/

I am just responding to your post. You said they could CF the APU with HD7770, but it isn't possible architecturally wise. Also, neither Sony nor MS would ever use a desktop-based GPU in a console. It will be a mobile version. For example, HD7850M uses about 32W of power, while HD7950M uses about 50W (that's basically a slightly downclocked HD7870). 

http://www.notebookcheck.net/AMD-Radeon-HD-7950M.72676.0.html

You also said MS's system could use FX8xxx CPU but as others have pointed out already, such a design decision would result in a very power hungry console without significant reducation in CPU clocks. Reducing clocks on FX8xxx defeats the purpose entirely as most games don't scale beyond 4 threads; and you'd end up with a very weak per core CPU if you downclock the FX8xxx to 3.0ghz or lower.

The only thing stopping MS or Sony from dropping ~ HD7870 (HD7950M) part into their next console is cost, not power consumption. A10-5700 + HD7950M would be a much fit for a next generation console for well-rounded graphics than FX8xxx + HD7770, but it sounds like Sony is now run by accountants not gamers. I at least hope they do include some kind of a dedicated GPU or the console is in trouble if the A10 APU is all that it has.

Even i don't think they will use FX8xxx,but if they use,you think develope won't make it scale beyond 4 threads?We are not talking about PC

1. AMD could have given them a higher discount on the CPU + GPU combo than going with IBM + AMD GPU separately.

2. You are overestimating the performance of Power CPUs for games. There is a reason Apple ditched Power in favor of Core 2 Duo back in the days, citing lack of CPU performance and per core performance necessary for applications. While AMD's CPUs are not faster than Intel's, even a $50 AMD quad-core CPU is faster than the CPUs in either Xbox 360 or PS3. 

In fact, the entire Xbox 360 Xenon CPU is only 70-85% as powerful as one Core i7 core (but Core i7 CPUs have 4 cores with 2 threads each!!) (http://www.eurogamer.net/articles/digitalfoundry-tech-interview-metro-2033?page=4)

The worst low-end AMD/NV GPU and the worst low-end AMD CPU deliver 30 fps constant in Dark Souls, something PS3 and Xbox360 can only dream of. That shows you how much lacking in power the Power PC in-order-architecture CPUs are. The more modern Power 7 is better but the CPUs in PS3 and 360 are extremely underpowered compared to even a $50 budget Intel/AMD chip.

$50 CPU + $60 GPU has no problem keeping 30 fps constant in Dark Souls at 2560x1600. 

http://gamegpu.ru/images/stories/Test_GPU/Action/Dark%20Souls%20Prepare%20To%20Die%20Edition/ds%202560.png

http://gamegpu.ru/images/stories/Test_GPU/Action/Dark%20Souls%20Prepare%20To%20Die%20Edition/ds%20proz.png

3. x86 code means it would be a lot easier and cheaper to develop games and port them from PC. You could make a PC game from scratch using common tools, and easily port the game to the console by turning down some settings. This worked well for Xbox 1. It would have been better if MS had gone with a Core 2 Duo CPU for Xbox 360 but such option was too expensive at the time. With AMD now selling decent speed CPUs for under $125, x86 is now back on the table.

4. The above are still uncomfirmed specs and rumors. For all we know, there is no x86 CPU switch. 

I agree about points 1,3 and 4.

About point 2, there are actually 3 points to answer:
2a) Apple mainly switched to Intel because IBM had no interest in developing also a mobile version of the G5, so MacBooks were stuck with G4 and going to become too underpowered soon. OTOH Intel always thrived in the notebook market and so always had the maximum interest in developing the best it could for that market.
2b) I agree that despite not always offering the most powerful CPU, AMD very often offers the best value from low to middle-high end (although on desktop Athlon was not only the best value, but also the most powerful x86 CPU from 1999 to 2006, and AMD was the first to extend x86 to 64bit and first in 64bit PC performances for some more years, but unfortunately during those years only Linux exploited that power, while mainstream Windows seriously switched to 64bit too late to help AMD).
2c) Basically, Power's scalability isn't enough, there must be IBM's interest in developing the right version, but there's also one thing wrong in the comparison you cite: the article is from 2010 and it compares the performances of XB360's Xenon, a 2005 mid-range CPU that given the timeline could be at best based on Power 5+, with Intel Core i7, a high-end 2008 CPU, that, BTW, at launch was very expensive, out of reach for a console with prices starting from less than $300, and at 3GHz it ate 130W, the CPU alone, when in 2008 a Jasper XB360 had a 150W power supply. And in 2007 IBM released Power 6, that for almost the same power consumption of Power 5 gives double performances.
But basically, Intel CPUs could offer neither the performance per Watt, nor per Clock, nor per Dollar of contemporary Power CPUs.
Edit: not to mention that in 2005 Intel, outside of notebook market, was still stuck with very poor CPUs compared to both AMD Athlon and IBM Power, it took Core 2 Duo for Intel to beat again AMD, as the first Core Duo failed by a whisker and before it P4 utterly failed.

It would be quite nice if Sony&Ms went for x86. Pc+xbox+playstation versus wii u as easy developer choice.

Why would one console being left out be nice?

Being that less than 1% (probably less than 0.1%) of code is written at a low enough level for the CPU instruction set to matter, I don't think all manufacturers using the same chip makers makes a big difference ... What matters is capabilities and overall architectures.

Developers would be happy to work with a 8 core x86, 4 core Power, and 16 core ARM processor if they supported the same number of threads (16) with similar performance per thread; and, in contrast, the single core Wii U CPU, 3 core XBox 360 CPU, and 1 Core+7SPE Cell processor was a nightmare for developers even though they all used similar instruction sets and were manufactured by the same company (IBM).