Rumors have put AMD behind the CPU/GPU this time, so it will be similar to other consoles.
Nintendo wants to absorb Wii U architecture to a point, I'm assuming this means eDRAM and espresso on an MCM for BC/VC.
Nintendo also wants to create a single platform with multiple devices, meaning a NintenOS running the same games on handheld and console.
A 2016 announcement and 2016 release for a new handheld shouldn't surprise anyone, however they could easily launch both devices next year, running the same games and positioning them as 2 options for the same purpose. The benefit here is that it really doesn't matter which product a consumer buys, they will end up in this ecosystem and spend money for Nintendo, so if the handheld is bought 10 to 1 or vise versa, it doesn't mean much for Nintendo.
Performance wise. The Handheld sitting at or beyond Wii U in performance is pretty likely. If we are talking about AMD, they do already produce an APU that is 128GFLOPs and uses only 2.8watts, considering the chip is developed on 28nm, and 2016 will see 14nm AMD parts, it is very possible to get above Wii U's 176 GFLOPs of performance in only 2 watts.
Best option for Nintendo is a 256ALU handheld clocked at 500MHz giving 256GFLOPs, running 540p resolution top screen at ~5inch. This would give them much more performance than Wii U, and at the limited resolution would be a noticeable step up even.
The console would then release with 8x the performance, this means 1024ALUs clocked at 1GHz giving 2TFLOPs of performance. The reason I suggest this is because it would run 1080p native games, performance would be slightly beyond PS4 in graphics performance while the CPU would trounce it, which is really PS4's Achilles heel. 8GB stacked memory and 64MB eDRAM.
DeNA is a huge asset for Nintendo if their business collaboration succeeds and considering the thirst for Nintendo on mobile, I don't see why it would fail, they would finally have their network and account system set up properly.
Lastly, they should use Game Cards like 3DS, but 16GB in capacity for both platforms, removing the disc component allows the console to be much smaller, gives the true impression that the handheld and console are the same platform, and allows for better marketing of the devices and their games... Not to mention the much larger shelf space. Giving devs options to put any game onto the eshop, and using SDXC cards would allow Nintendo to have giant storage space for their handheld and console without having to rely on frankly dated disc technology.