It doesn't seem like Nintendo is keen on replacing the 3DS quite yet. Their comments about the larger installed base and being able to sell to it at the Investor Briefing make me think we're getting a console first. Your suggestion would be a very interesting device to release late in 2017, though, especially if the shared library comes to fruition and people can play Wii U levels of fidelity for Smash Brothers and Breath of the Wild on their portable.
I agree, and I fully expect that what we're getting in March is a home console (particularly due to Nintendo specifically citing the existence of NX as a cause for the drop in their Wii U forecasts this FY), but my point was more that they probably could release a handheld capable of running Wii U games like Zelda:BOTW in early 2017 if they wanted to, without having to sacrifice battery life or charge an extortionate amount. Late 2017 seems a more sensible timeframe, though, particularly as 16nm matures and becomes more affordable.
It's doable in a console, but requires separate chips for the console and handheld. Of course, Thraktor is assuming a 28nm Maxwell chip here so I don't know how well the cost would really translate to Pascal, which I still believe that they're using. I can't see Maxwell because it would require nearly twice as much power as Wii U and I honestly don't think 16nmFF+ costs as much extra as Thraktor believes. Either way, if that analysis is correct and we throw in a card slot in place of an optical drive, even with a not-so-cheap gimmick we can come in at under $300 while outpacing PS4 handily... So, expect a $200 machine which can't touch Xbone but nets a healthy profit.
Edit: Well, this is before considering that the costs of 8GB LPDDR4 and the cost of storage (unless they skimp again), so it would actually still lose money at $300... Welp.
Nope, my calculations are all based on Pascal* on TSMC's 16nm process.
Besides, 8GB of LPDDR4 (or whatever other memory they were to use, sans HBM) wouldn't be prohibitively expensive for a March 2017 release, probably around $50. On the storage side, the 32GB of UFS memory used in the S7 cost just $7.25, and even if (a) there were no returns to scale on flash and (b) cost didn't come down at all in the year since the S7 release (both blatantly untrue) they could still get 128GB of (very fast) UFS flash for $29, less than the HDD cost in launch PS4s. More realistically, they could probably get 128GB for under $20 and 256GB for under $30. Without mandatory installs, and with USB3 external storage support, either of those would be perfectly satisfactory.
All in all, a $50 SoC, 8GB of LPDDR4 and 256GB of flash should be entirely doable for a $250-$300 console with no disc-drive and no expensive additional features.
*GP104-style Pascal with 128-core Maxwell SMs rather than GP100-style "true" Pascal with 64-core SMs.