IMO an AMD SOC is very likely, if not all but guaranteed at this point.
PS4 levels of performance allows for games like Horizon Zero Dawn in an open world, TBH if Nintendo used 8 of AMD latest mobile CPU cores, like Puma, along with a 1.6TFlop GPU they'd be capable of doing that, with a chip that uses less power than PS4's SOC does.
PS4 games, particularly exclusives are going to be heavily built around physics and a lot of general compute being offloaded to the GPU, Nintendo may take a difference stance and add a more capable CPU, which would also be capable of handling a lot more physics code, overall a different kind of balance, but plenty of GPU hardware to deal with the kinds of games that will be made over the rest of the generation.
AMD's most current CPUs are much more capable than their Jaguar tech, developers wouldn't have to offload as much general compute code to the GPU in NX.
Of course a more powerful GPU would be all gravy, overall NX could have more than 50% greater performance overall compared to PS4, but still use less energy, even at 28nm.
28nm seems pretty likely as it's mature and cheap, 14nm would add cost.
I think anyone trying to legitimate figure out what level of performance Nintendo could use in their next console really just needs to think about form factor and cost.
Nintendo can put themselves in a good position with developers by just packing a better CPU in their next console and a GPU with a new feature-set, but similar levels of performance to PS4 or even somewhere between that and XB1.
It's possible Nintendo tries to release a home console that can handle the level of multiplats you get on PS4, but at 1080p 60FPS, since that badge seems pretty important to a bunch of people this generation.
Nintendo launching this at the end of 2016 would make sense as it has the potential to take some of the wind out of the sails of PS4 and XB1, especially if a Nintendo home console also offers a decent array of exclusives, while also running multiplats at the best level compared to the competition and Nintendo can get just as much support as the competition does.
Not to forget that NX is most likely going to offer gamers the ability to be able to buy a handheld so they can take any of those games anywhere they want and continue to play everything on the move, that's a pretty unique prospect.
I know PS4 allows for Vita to be used for remote play, but games don't run natively and you require an internet connection to do it, NX would be an all native thing, so no latency problems.
