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.
Well, looks like I was wrong. Rumors point towards a switch revision towards the end of 2019.
Though I predict this to be a New 3DS type thing. A more efficient Switch, with a Nvidia Tegra X2, and improvements in places such as screen quality and battery life. I expect this to completely replace the original model (so it gets discontinued as soon as new model launches).
However,I still stand by the other half of my prediction. I maintain the new Switch will retain the almost the same form factor and size. No XL model, no mini model, no TV only model, no budget lite model, no pro model. For the reasons stated in the OP.
At any given point in time only one type of switch will officially be sold.
Bet with Intrinsic:
The Switch will outsell 3DS (based on VGchartz numbers), according to me, while Intrinsic thinks the opposite will hold true. One month avatar control for the loser's avatar.