The Switch has proven to be quite successful, and we all know what successful things all receive, Sequels (not always, but you get what I mean).
What features would you personally want a Switch Pro (or other revision) to have, be as selfish as necessary; but be reasonable (no GV100, 4k portable).

For me:

•     I want a 1080p or better screen, OLED would be nice.
•     802.11ad WiFi for peer to peer connections, especially if Nintendo wants to enable us to download updates from peers.
•     Metal Joycon rails, I want a more sturdy device.
•     A better kickstand, hey maybe even add a second one...
•     Decreased bezels, either reduce the device's size or increase the screen size.
•     Maybe a second Micro SD card slot.

What features do you want?

Everything about this is premature

Is 1080P on a 6in LCD really going to make a noticeable difference?

It is actually, but the screen would be more like 7.25inches if you remove the bezels, so a higher resolution helps in keeping the same/better PPI as the current Switch. 

Plus it would be good for VR if Nintendo wants to try that. 

Yes.

How about we get an HDR10 display that also supports variable refresh rates ?

-Exactly same size(to fit in any dock) , but bigger screen.
1080p.
-Can run in regular switch dock mode performance (even when undocked).
-User can select if use performance more performance (like docked regular switch), or battery save(that perform like regular switch unlocked, but upscale to 1080p), that would increase battery life in 50%.
-VR accessory included(just a piece of plastic, where you put the switch and in your head ), VR is exclusive to switch pro, due to resolution.
-launches same day as Mario kart VR.
-2019, uses x2,  allowing to reach the clocks of regular switch docked while in undocked mode. 300$(mini switch launch earlier same year, with same technology, but smaller,  at 200$)

- without screen
- without dock
- without controller
- without battery
- without storage
- without plastic
- with a download code for a Nintendo PC client

I think we could see a Pro or Mini at the end of 2018 (one for the holdays and the other in March 2019), I would buy both for sure.

The Switch Pro you propose is appealing, but an oled screen plus a potential decrease in size for the unit.....that battery life isn't looking too good.....

My concept would be a Switch XL
-The screen will be 900p (not because of pixel density increase, but just screen enlargement)
-screen size would then have to be 7.75 inches
-the size of the unit will be only very slightly larger since bezel thinning will compensate for most of screen enlargement
-add in the things you said (second kickstand, metal joycon rails, 2 micro sd slots)
-64 gb storage
and there we go.

edit: make it use the tegra X2