It doesn't need to be on par with the modern stationary home console, but a 1 generation gap (which is a lot still) should be the most they should allow. 

It's not a Game Boy or DS or Wii either. It's not something that's going to sell off "being cheap + kids + casuals" either. 75% of Switch owners own a PS4 or XB1, these are core players, Switch is a high end product for a portable machine, there's never really been a portable that delivers full scale console type experiences before that don't feel like they're 10+ years behind what's relevant today. 

Pokemon Go doesn't look that great, but the Pokemon producer has already said Gen 8 will look considerably better, and Zelda BoTW, Mario Kart 8, and Mario Odyssey ... you could put any of those games in 4K resolution on PS4 Pro or XB1 X and people would happily play them and not really make a big fuss about the fidelity. 

Doesn't look far off from this on PS4:

Is still at least somewhat in the same ball park, it's not DS to PS3/XBox 360 (a two generation gap). 

Well they they will not wait until 2023/2024. without any revision, New Switch, Switch Pocket, Switch TV, Switch Pro...are all possible revision for current Switch. We most likely receiving first revision next year.

They don't need big hardware boost to maintain good sales with their revisions in any case, hardware strength is not what selling Switch on first place. They will maintain sales with price cuts, revisions and new releases, like they were doing with 3DS for instance (just with big difference that Switch is and it will selling better than 3DS in any case).

Adoption of 4K TV is getting much faster, and in 5 years 4k will certainly be standard, also upscaled 1080p on 4K TV doesnt look too good. I dont expecting that Switch 2 will have power to push native 4K, but some some higher resolution than 1080p that could upscale much better to 4K (maybe 1440p for docked mode) is very possible.  

Sure Switch 2 would be much stronger than than that, I mean 2-3x more power is possible even now with just Tegra X2 instead of Tegra X1, and who knows how much strong mobile chips we will have in around 5 years.

The Wii was basically upgraded GC (its same GC hardware just overclocked with motion controls), but Wii U defintly is not improved Wii, it has improved CPU, much modern GPU, more modern and much more RAM...Wii U is true next gen compared to Wii, same couldnt be said for Wii compared to GC.

I think you're placing too much weight on the largely mythical "hardcore vs casual" dichotomy. The real world is not that black and white, most consumers are neither forum-going "hardcore" gamers nor stereotypical "casuals" but some shade in between.

The point remains the Switch is a new kind of product even by Nintendo standards. The concept is not just appealing because it's a "Nintendo system". The whole idea of a "portable console" in itself is appealling. And we see surprising stuff in Switch software performance, like Diablo III outselling the new Nintendo Labo kit, lol. Which is fine. That's exciting, who the fuck just wants to keep repeating the DS again and again. 

That whole philosophy of using the lowest end hardware won't work any more because smartphones cornered the market on cheap/low end software. And that's fine too. Nintendo games are (believe it or not) while not necessarily requiring the best hardware, still better on better hardware. I wouldn't want to play Mario Kart 8 on the Wii or 3DS, sorry. 

But can we really look at a system that's flying off shelves on the back of Pokemon Let's Go, a game that would've looked outdated in 2012, and surmise that being technically up to date is one of the system's key selling points? I think we're just going to have to agree to disagree here.

Switch was successful long before Pokemon Let's Go was announced though, that game is simply just carrying momentum the system already established 16 months prior. 

And games 4 years from now will likewise simply carry momentum established by the evergreen killer apps of now, next year, and beyond. They can look as outdated then as Let's Go does now and it won't matter.

Im expecting new updated versions of switch ever 2 or 3 years starting with the new on next year.

On the same system? I doubt it. Not unless Nintendo is OK with yearly shipments in the 5 million/year range. 

You're turning the Switch into the 3DS if you're just going to let the chipset age that badly, and IMO the sales appeal will drop to a more narrow audience. 

By the end of 2019 alone, Nintendo will have burned through the following franchises:

3D Mario, 2D Mario, Smash Bros, Zelda, Mario Kart, Pokemon Lets Go, Pokemon Gen 8, Animal Crossing, Fire Emblem, Splatoon, DKC, possibly Metroid. 

That's pretty much most of their A/B-tier roster. That's also a big issue. Yes you can make a Mario Odyssey 2 or Mario Kart 9 even, but you're not going to get large hardware boosts in the same way because large portions of the fan base for that IP will already own a Switch. 

A new Switch model with a legitimately higher end chipset that is comparable to what the XBox One X and PS4 Pro (2-3x the power of the base unit) around 2020 are to their predecessors will boost Switch yearly sales, there's just no way it won't. From a business POV it's the right play. 

There's not even any loyalty that you get from the "we want 5-6 years of support no matter what!" crowd, did Nintendo get any loyalty for supporting the Wii for 6 years? Nope, that audience base dumped them like a bad habit with Wii U. Supported the DS for 7 years, and lost half their market with 3DS. You get really very little "bonus points" for pleasing a very small portion of the overall consumer base. Yet everyone and their grandma bought a DS after they only supported the GBA for 3 years.

Well Nintendo appears to have given up on the home console... so I imagine another Switch type of device.

Except it only does red, it will push 3D and it straps to your face. It will be called Super Virtual Boy.