Many people think a Switch Mini/Switch XL/Switch TV will come out in sometime during the Switch's life-cycle.

However, based on Nintendo's past consoles and compatibity and marketing issues, I dont think any of these will ever come to fruition.

If a switch Xl happens, there will have to be bigger joycons especially for the XL, leading to mass confusion and people pickking up the wrong size of joycons. The dock would also probably need to be widened, leading to two different types of docks. Okay, I see someone saying that they could just get rid of the thick bezels and replace it with screen to get a significantly bigger display, However, that would straight up kill the battery life. Since the console is the same size and will probably have the same size of battery, that same amount of battery running an even bigger screen would shorten the battery life eve more than how it is now. Also, a question in general, isnt 6.2 inches big enough for a handheld? A bigger size will only make it less portable. If you want to get a bigger screen, all you have to do is hook it up to your tv. Simple.

Now, Switch Mini, if youre supposed to be able to dock it and detach joycons, it faces the same probem as the XL with the different size of dock and joycon, causing mass confusion. However, the more common pitch I've seen is this: "Portable only, undetachable joycons, a bit smaller, for $200, and this will open up the switch to an even bigger audience".

There are a few issues with that. First off, this is quite redundant for a budget product since youre now paying $60 for portable only games (unless they make seperate versions for the mini, which would again cause huge confusion and would be too complicated). Secondly, this wont sit well with the console's name and its tagline: "Switch and Play".  This model will be sorta contradictory to what the Switch was set out to be. And the biggest point of all is: "So you want a handheld that plays Nintendo games and is significantly cheaper than the Switch? Than the 3DS ids for you". You see, the 3DS family is already that budget system that people want Switch Mini to be. And yeah, I admit that the 3ds is waning and on its way out, but by the time 3DS gets dicontinued (circa. 2019), the Switch would already be hitting $200, really not having a real need for a budget version of the console by that point.

And to the people who think Switch TV could happen:

And lastly , lets take a look at Nintendo's past consoles. The Wii U didnt have a console revision. The Wii only had a slight revision where all that happened was that it lost Gamecube compatibility and bacame horizontal rather than vertical. The Gamecube didnt have a console revision. The N64 didnt have a console revision. Nintendo hasnt had a significant change midway of a home console cycle since the SNES. 

I think at most the Switch will get a slight tweak that improves build quality or adds a 64 gb drive or somthing like that, but not much more than that.

But who knows, maybe this all blows up in my face and all three models get released. I am no expert and this is pure speculation at the end of the day.

Thoughts?

EDIT: 

Well, looks like I was wrong. Rumors point towards a switch revision towards the end of 2019.

Switch TV won't happen, Switch mini will happen because the Switch is a handheld at its core

There will absolutely be some sort of update, even if it's just a lighter, thinner model running on a more efficient chip. A Switch Lite, if you will, or LightSwitch.

There will be some sort of revision focused on the handheld aspect of it. Every single Nintendo handheld has had those. Bigger/smaller screen, more power, better graphics, lighter console... it's just practical stuff to improve a handheld's lifespam.

For a long time before the Switch released, I thought it was more likely that the Switch would have a Switch TV iteration than a Switch mini iteration. I can't really justify that feeling anymore ... but I will say that making a Switch mini is a lot harder than people give it credit for. Besides the black boarder around the screen, there's not a lot of cleanup you can do on a Switch. The screen should be an appropriate length for the console itself. It would not be very practical to make the screen smaller, even if it's just a bit smaller. The controls on the handheld form are already pretty compact too. That being said, there will probably be a Switch mini. 

This is the same kind of logic that would lead someone to rule out the possibility of a 2DS.

All Nintendo handhelds get revisions. The market demands it; it was always a revision, not the original model, that comprised the largest portion of Nintendo's handheld sales.

There will be a smaller handheld only version with non detachable joycons.
There will be an upgrade with larger screen (smaller bezels), and more efficient components that can always run at docked power level.
Dunno about a Switch console versions, but I don't see a reason why not down the line. Heck the components should fit in a usb stick in a couple of years. Switch stick.

The 20nm fabricated tegra chip may not even be possible soon. Fabrication doesn't stand still. Many revisions are practically forced on the manufacturer because the main chipset has to be updated to the newer fabrication. So there will be an internal revision at the very least unless they build too many and end up stockpiling them like the wii u but this seems unlikely with the Switch level of demand at the moment.

Updating home consoles is not the same as portables. It makes more sense to update portables in many ways because newer fabrication actually improves the product by extending battery life, lowering weight etc. Often Nintendo does a slightly crap first portable and then introduces much improved versions later and this is likely the case with the Switch. Who doesn't want a Switch with better battery life, more compact and at a cheaper price?

From the same company that has 6 different models of the 3DS in 6 years. Sure.

And that is where your argument fails.
The Switch is not like any of Nintendo's past consoles before, in the fact that none of them also functioned like a handheld. And every single Nintendo handheld, from the 3DS all the way back to the original Game Boy has had multiple revisions and variations.