Of Course there will be only handheld Switch, smaller and lower price point Switch. Nintendo will want to bring Switch gaming to masses with lower price point same they did with 3DS (3DS curently has price point from $80-$200), and to have something for some 3DS users that will want to upgrade but not paying $300 after 3DS dies.

That plan is very logical and actually great plan because there is no much sense (espacily we know all things Nintendo is doing) to release another handheld after 3DS that's not part of same Switch unified platform and that doenst plays same games.

Except it completely shoots the concept of the Switch in the ass and makes the name completely meaningless and muddies the entire message.  A 3DS is a DS system.  It's in the name and the core of it remains with the 2DS.  A Switch handheld would be a messaging train wreck.  "Hey here's the latest iteration to our popular Switch line!  It's a smaller Switch that completely eliminates the feature upon which every single aspect of the product is built, from design to the very name!"  Seriously, how do you even market a Switch that doesn't Switch?  That's not a gimmick like 3D, that's a core pillar of its whole design philosophy.  

And again, the 2DS has been a pretty modest success compared to the New 3DS so I'm not sure they would consider that philosophy worth following again.  And also again, the 2DS retains all the 3DS's core functionality.  The Switch being smaller and handheld only would eliminate all splitscreen gaming, all TV gaming, hamper online gaming potential, reduce the viability of large console games that really need that bigger screen to be worth playing.  It would compromise the cornerstones of its design, the very elements that make it desireable in the first place.

It would be far, far, far wiser to simply pursue discounting the base Switch as time goes on - which word is they already are planning ahead for - and then focus on a Switch Pro iteration to shore up its position in the console space.  

I think that a Switch "mini" doesn't necesarily has to renounce to the TV connection: Just sell a cheaper SKU without dock, better batery, but make it compatible existing docks, even if it can't improve the game performance when docked. Docks are sold separatedly, aren't they?

Nothing that Switch "Pocket" name for instance couldn't solve. Its not really so complicated or hard to understand, smaller, cheaper Switch just for handheld playing, its very simple and easy to understand.

Switch "Pocket" or Switch "Mini" would bring Switch to people who dont want to pay $300 for Switch, or dont need home console side of Switch, or just want smaller Switch with better battery for handheld playing.

Along side Switch Nintendo curently has lowerd price products with New3DSXl/New3DS/3DS/2DS, when 3DS dies Nintendo will definatly want to have something instead 3DS line with price point of $200 or lower for start, no way they will just have $300 Switch on market. That doenst mean there will not be Switch "Pro" or Switch "Home" down the line, but we definatly getting Switch "Pocket" or Switch "Mini" first because it's far more important for Nintendo to have something in similar price point because 3DS is most likely dying next year.

I have my share of doubts that Nintendo will release something like that. First, a smaller form factor will need also smaller Joy-Cons, which are already pretty small for most people.
We cannot determine how full of tech the device is, but making the already expensive HD Rumble even smaller, will only increase the cost.
Same goes probably for the display with a higher ppi, unless they reduce the resolution which all the games has to be also adjusted to it, meaning larger text and HUD.
A smaller device will come with a smaller battery. So, by having the same specs, the portable fun time will decrease.

So, making it smaller and cheaper will probably not be possible.
But, the current Switch is already open for a price cut.

There will be a Switch Mini but it won't be portable only. It will just be a smaller version of the current Switch, but it'll do the same things.

Removing the plastic dock simply doesn't save you enough money in real manufacturing cost to bring the price down much. 

They have lost a possibility, for instance, they can easily release Switch "Mini" without Joy Cons, or whitout some HD Rumble, or built in Joy Cons, in order to have more affordable price point.

Display isn't problem in any case, having 5-5.5" with 720p resolution is very easy to imagine, I dont think there would be problem with text or HUD.

Smaller device would come with smaller battery, and smaller screen uses much more less battery than bigger, and they can certainly cut some staffs because device wouldnt run in docked mode like regular Switch.

On the contrary, making Switch smaller and cheaper just for handheld gaming is very possible, and actually almost certain thing that Nintendo will do.

Going with a lower battery really doesn't save that much. The difference between say a 2500 MaH battery and a 4800 MaH battery is like maybe $3-$4 of savings at a manufacturing level. 

Ditching the Joycons would save them money, but I don't think Nintendo will be willing to do that, it may also cause compatibility problems, like what about games that use custom Joycons? Or motion control? Or the IR camera? 

3DS - 2DS didn't make games unplayable, such a revision would however. 

What's the point really anyway? The plastic HDMI dock is dirt cheap, and even if they're dumb enough to not be able to figure out how to make an HDMI dock cheap, they could just figure out a cheaper way, or just the USB-C to HDMI cable. Simple, cheap. 

There is no point to release just smaller Switch and having larger on market also, especially if there is no price difference between.

Its not only just about dock, for istance Joy Grip also, cables, Joy Cons can be bult in, also they can remove some staffs beacuse it want be runing in docked mode, smaller screen and smaller devaice...I think they can esily make Switch "Pocket" or Switch "Mini" just for handheld playing for $200.

If if doesn't come with the Joy-Cons then how do you control this thing?

Removing HD Rumble could also lead to not being able to play certain games, like 1-2 Switch. I doubt Nintendo will limit your gaming options with a smaller device.

If you go for 720p on a smaller scale, you increase the PPI which increases the costs. And it still "could" need a redesign of text, because at some point it would be too small to read.

So, you want the switch mini to be handheld only? Uhm... then it wil be an entirely different device altogether.

edit: Well, you are definitely going for a different device than the switch is. So, instead of wanting a Switch Mini, you want an entirely different portable device from Nintendo, which is not compatible with the Switch library.