It's possible I think if they have more hardware versions and different classes of hardware, thus basically incentivizing people to buy multiple Switch systems over the same 6 year period that would define a normal "generation". They can bend the rules there, much like tablet makers and phone makers do, as almost no one keeps one phone for like 6 straight years.
I think you'll see the current Switch die-shrunk to a more efficient 16nm chip, and eventually that model will be smaller + cheaper and Nintendo will target that to a younger audience, but by mid-cycle IMO they'll have a higher powered Switch to replace the top end of the market (2DS/3DS likely completely gone at that point).
They can do this much more easily now too because Nvidia because continues to iterate up on the Tegra chipset, so Nintendo doesn't have to pay a ton for R&D or shoulder the R&D burden themselves.
Yeah, I certainly think they will do redesigns (and a more powerful Switch that basically plays the current docked mode in handheld mode would be too obvious of an opportunity to pass up on).
As for your other post: I believe the Switch will sell very well to women once the price goes down and the right software releases. You can't have a breakout hit system without women, as women have about 80% of all purchasing power ("pitch to the b*tch" is what they teach you when you want to become a salesman). And I don't think smartphones will change that. Two months ago many people thought handheld gaming was dead because customers in general had moved on to smartphones. Apparently, they haven't. And once the software hits, women will be on board. I just recently read that Nintendo was very pleased with the 2DS because it sold so well to women and children and women are certainly the target audience for the 2DS XL. Nintendo has always seen female gamers as a very important market and they won't stop to release the right products for them.
You can have a break out hit system without women.
Playstation 4 is going to surpass the Wii easily. Heck, if you really look at it, the Playstation 3 even nearly matched the Wii despite a disastrous start at $600 that basically nullified its first year on market.
Switch is also already proving it, it is outpacing any other Nintendo system in sales. It has appeal to core gamers that Nintendo hasn't had in decades. It looks cool and it's relatively high end for a portable device.
Switch is very different from the Wii and will continue to be throughout it's lifespan. And that's OK. This notion that Wii is the only way to ever sell anything with a Nintendo logo on it is simply not true. We are seeing a Nintendo system where Just Dance sells like shit and 1,2 Switch is not really breaking out at all as a big hit still breaking records.
Some of the audience base will be female sure, as I'm sure PS4 also has a decent take of women too. But it's never IMO going to be a huge driving force, and that's OK. People forget actually that Wii is not the highest software attach rate for a Nintendo system, it's actually GameCube (yeah go figure). If Nintendo can have a system that has the attach rate of the GameCube but has 4-5x the hardware base, which I think is in play because of portability for one, that would be huge.