If the chip comes in 16nm already, there's no point in porting it back to 28nm, as this would make the chip much more expensive as it would use up almost 4 times as much space on a wafer - and thus having less chips per wafer. Since chips are sold per wafer, it would drastically increase their cost. Besides, the bigger chip would also consume more energy, possibly too much to work at the same clock speed as the 16nm chip.

If they would still be using a chip in 28nm from AMD, than it's probably a Puma (+) Processor (an evolution of the Jaguar in the PS4/Xbox ONE), since the Bulldozer based chips wouldn't work well (read: even worse) in a console, and a GCN 1.1/1.2 (PS4/Xbox ONE: 1.0) graphics chip. In both cases, the evolution upon the hardware in the other current-gen consoles is pretty weak, meaning Nintendo won't be able to come close to PS4 power unless they would more than double over the consumption of the Wii U. Since Nintendo has stated they prefer to build small, I doubt they will do so, as the extra power would need extra space for stronger cooling and heat dissipation.

So, either 14/16nm or along the line of Xbox ONE power at best. Unless they'd use 2 seperate chips for CPU and GPU, allowing them to mix 2 different production processes. But that's kinda pointless if the producer delivers both in a neat all-in-one package.

If AMD is so great, why does no one in mobile use them? I doubt AMD can give Nintendo the same power per watt for the same price PowerVR can. There's a reason Apple banks on them. A8x does get warm, but it works and works fine and is in tens of millions of devices, mass produced at 20nm without too many hitches since last year. 

Funny thing is, they actually do. Never wondered why Qualcomms Graphics Chips are called Adreno? It's an Anagram of Radeon, bought from AMD in 2009, and the Chips are based on then-current VLIW4 (Evergreen 2) Radeon Graphics Cards architecture.

AMD could in theory go back into mobile hardware, but they would need to divert much money and manpower from their other hardware products in order to do so. And since both are in pretty short supply at AMD, they backed out and never went back again.

I can definitely see Nintendo using a similar setup for NX but what I want most is for Nintendo to try out the Nvidia Tegra X1 since it has support for ASTC and is equivalent to Microsoft DirectX feature 12_1 ...

Tegra X1? That one's coming with the Shield Android TV (formerly known as Shield Console) already. So you could basically expect the NX' eShop getting flooded by shoddy Android ports as porting would be super-easy. Not exactly what I would want for a Nintendo console.

I doubt DX12_1 will have much impact, just as did DX 10.1 before (where AMD had the lead btw).

I don't think you can claim that just yet or anymore since Qualcomm has been adding a ton of their own changes and their pretty secretive about their own GPU ISA ... 

Nintendo can still control what goes into the eShop so I don't see why your worried there ...

It won't have much of an impact as far as third parties go but for Nintendo themselves it's a HUGE advantage and let me tell you that feature level 12_1 is not a small step up compared to 10_0 to 10_1 or 11_0 to 11_1 considering the awesome techniques you can do with it ... 

Feature level 12_1 isn't all they're getting. Their also getting multi-projection acceleration and sparse volumes ...

I doubt anyway that the Shield console will be a success. 200$ for the base version and 300$ for the pro (the difference being a 500GB HDD instead of 16GB Flash) sounds absurdly expensive for an android console, no matter it's power.

As for the DX 12_1 functions, I still doubt it will change much, no matter how useful these functions are. Besides, we will have to wait and see first if these are implemented fast by games or if it takes years again before the transition is made.

The Shield Console is irrelevant ... 

Now that I think about it, I doubt Nintendo will ever use those advanced features in the near future cause I think they need to get some more of that engineering talent from regular AAA developers like Naughty Dog, 343 Industries, and DICE or whatever you favour ...