I really hope they don't dump the Switch for another new crazy idea (unless tech has changed a lot by then). I love the concept of the Switch, really fits in with my life (basically fucking off and not being in front of a TV all the time).
I have to agree, and I have pointed out before that I have surprised myself with how nice I've found it to simply be able to play a game in bed, or in a particularly comfy armchair, or out on the porch, never mind on trips. The freedom is seductive, and it now feels quite restrained to
have to be parked in front of a big screen, even though it is nice under certain conditions. My kids are young and they've asked me why wired telephones exist.
It's a good question.
Nintendo is interesting precisely because they can and will do the unexpected or unprecedented with the aim of creating novel gaming experiences (while being quite conservative in other respects).
However, one of the main driving forces for Nintendo to take the Switch path was so that they could unify their game development resources, rather than split them between platforms. I would guess that this would be a quality they would like to keep, if they feel the Switch works out for them.
Assuming this, they can't do much to improve the mobile platform until they have access to new silicon. It barely makes sense for them to move to (16/12nmFF) even though that would yield power draw benefits. I would assume that they wouldn't want to commit to new silicon before they know how the uptake of the Switch seems to be going, and if they were to commission a new SoC on 16nm, they would have to make a financially big commitment (probably already) with relatively little to show for it. 7nm seem like a better node for a mid-life bump of the design. Just transferring the design would drop die size to roughly a third, which would save them money at high volumes, and power draw would likewise drop to a quarter or so, which could be used to both extend battery life, and to get rid of the cooling fan even for docked mode. They can't make the actual device all that much smaller if they want to keep the joy-cons and the screen size. They might bump the performance slightly for increased pleasantness, but not enough to create a new platform. Apple will ship a few hundred million A11 SoCs built on TSMC 7nm, but will according to current plans move on from there to the EUV enhanced version in 2019, and to 5nm in 2020. So - 2020 could be a good year to introduce that 7nm mid-life kicker, and the Switch platform would extend to 2023 or so, similar in life time to the 3DS.
Another route though would be to follow the pattern of Sony and Microsoft, and introduce a distinct new but compatible product at around the same time, keeping a similar die size to the current, yielding a 3-4 times performance improvement along with hopefully a corresponding factor of 2.5-4 in RAM bandwidth, on board solid state storage and speed and so on. That would simplify multiplatform ports, and extend the valid lifetime of the console a bit, which could be a good thing in the foggy uncharted waters of a future where Moores law has severe difficulties, VR and AR may or may not come down in price and size, consumer habits may shift, and China may stop lending money to the USA. Making predictions now about the gaming landscape of 2023/2024 takes some serious crystal balling. Introducing something more powerful but backwards compatible on 7nm around 2020 synchronises nicely with stationary console upgrade cycles (for ports), and maintains a safely extended software environment for consumers as well as developers.
These two paths would make sense, and fit the time constraints of access to suitable lithographic nodes at reasonable cost for Nintendo volumes. But as I said in the beginning, Nintendo makes their own future.