Found some research on GAF and wanted to share...

If this were ventilation apertures, maybe it has a fan.

More evidence that the spot indicated by the blue arrow in that pic is an air intake.

The air intakes seem to be on the lower back of the tablet , the car mount is cut to accommodate them:

http://www.neogaf.com/forum/showthread.php?t=1297136&page=26

Well, a tablet that can play Zelda BotW without any extra hardware must be pushing itself very hard, so of course it's going to be hot. Will this be the first tablet with active fans for cooling?

It is still odd bc the nvidia shield console (the latest iteration) and the google pixel C tablet are not actively cooled.

What could that mean:
1. It is old, cheap tech (22nm) and needs cooling?
2. It is new tech, but highly clocked (1 TF) and needs cooling?
3. Docking power mode confirmed?

That is my belief.

Docked its cooled by a fan inside the dock, and because it is plugged in, it doesnt need to worry about battery life.
So its clock rates are "max'ed" out.

Undocked, and its cooling is less, and its gotta worry about battery life so it clocks down.

If it's at least as powerful as the Wii U, then it makes sense..

Even the 3DS can get pretty warm playing certain games

Makes sense... Air comes through the bottom and goes out through the top since thats how good airflow works.

I am thinking the fan will be a blower style fan

Jesus Christ people, even if it were to be using a Tegra X1 it would be much more powerful than the Wii U. 

I really hate fan noise. I suspect it will be quite loud. At least the Switch does not have any noise from disc drives.

Here more evidences:

Emily said so, in september:
-Cooling is still a little noisy
https://arcadegirl64.wordpress.com/2016/09/02/rumor-what-should-we-expect-from-the-final-nx-product/
(she got everything right from switch from what we know, so im believing)

It's basically certain that the NX will be stronger than the Wii U, but I like to be cautious in what I write ;)