Internal HD space is important to gaming. There's third party games already out that require you to buy an extra microSD card just to play the game. It might have been better to cheap out on something else if they were concerned about the price. 

I see a lot of Switch variations coming in the future, with more/less storage space, handheld-only/dock-only, bigger screen/smaller screen, etc. So, this coming wouldn't surprise me at all.

People were a lot complaining about the vita memory cards. Your last sentence even covers it. Xbox 360 was different because basically 10 years you could get for 50 bucks a 60 GB upgrade, 6 years ago for 80 bucks an 128 GB version. And now they ask 130 bucks for a 4 TB external HD:
 https://www.bestbuy.com/site/seagate-game-drive-for-xbox-4tb-external-usb-3-0-portable-hard-drive-green/4861900.p?skuId=4861900

You probably can go lower for a not official one.  If it is possible they should make an option to put external HD's in the system it is so much cheaper, Make Nintendo official External HD's that come with a game and people would eat it up.

Yeah I believe they will hence the daughter board in the design. It maybe driven by the fact a new flash memory supplier offers a cheaper new chip. Retail prices often take time to adjust but a manufacturer with a new design with a new fabrication process may suddenly offer a much more competitive product on price but requires new circuitry. Nintendo designing the Switch with a flash memory daughterboard clearly wants the option to use any cheaper flash memory that becomes available and will redesign the daughterboard accordinly. That may be simply a 32GB model that is cheaper to make or a upgraded 64GB model that is only marginally more expensive than the 32GB model to manufacture. If they can increase the retail price too or use it to justify continuing with the same retail price it makes sense.

It's possible we hear of a minor revision before Christmas but more likely into 2018 and the further into 2018 it is probably the more major the revision will be. The 20nm fabrication process is getting old hat now anyway and they are going to be forced to move to a better fabrication process at some point just like the 360 and PS3 were in their time. Fabrication process doesn't stay still. It's not like you can ask a I.C. manufacturer to make you 90nm chips nowadays they have long since moved on. How long can a manufacturer stay on the same process? 20nm was old when Switch launched. My windows tablet is on 14nm and its older than the Switch by about a year.

My point is they are going to be revising the Switch motherboard at some point to take an updated Tegra chip. Maybe the delay in getting more Switches to market is simply they have to ration Switch's until the new model is ready. They simply don't have enough 20nm Tegra chips. They certainly wouldn't want to announce this because sales of the current model would plunge with everyone waiting for the version with better battery life. The revised model could also benefit from greater storage or there could be a premium version.

Switch uses Micro SD and anyone can very easily increase memory of console if that is needed.
Actually Nintendo is counting that users will use MicroSD like expansion of memory in any case.
So there is no need for Switch with larger internal memory.

Definatly not gonna happen (best you can hope is 64GB), bu if you really want 256GB storage just buy 256GB Micro SD card. And I also doubt we will ses 4G model.

Storage is totally different compared to more power or ram, because storage can easily be increased by users if they need.