The WiiU Controller is not a tablet in a way that it does not have the same specs as a tablet. Therefor it can not be compared to a tablet. It's just a device with visual output and touch/buttons/sensor input. All the processing is done by the console. It only sends and receives data. By the looks of the controller it has enough room for a large battery. So i say 8-10 hours.....maybe even 10-15 hours.

Agree.

But then there are all the things that affect it like how bright we set the screen (if we can change it, ofc), the volume of the speakers, if the game uses the motion sensors or not, etc.

10+ hours.

Yes,

but due to the fact we don't discuss about a real tablet I'm confident.

Should be a lot, why would they limit it so much?

Like Edan said, the actual power comes form the WiiU. The controller itself will not create the images, but it'll stream them from the WiiU. That alone should give it more battery life than a traditional tablet.

10+ hours easily.

Nintendo better provide a charger for it, though. I'm tired of having 3rd party chargers.

at least 8 hours would be ideal.

Considering "most" of the time Nintendo strives for a very long battery life (original GB and 3DS are exceptions), I'd bet it will have a sizeable battery and get a good 15hrs of play time at least.

idc how long it lasts, aslong as we can recharge it, I want to link it to the console for recharge like the PS3. Hated changing the batteries of my wiimotes over and over again and imo the 3rd party rechargers totaly ruins the look of my wiimotes.

This one is a good question, and an important plus limiting factor for the controller. The device itself is designed to consume the least possible, but having a dock where it can charge up while not being used and have an auxiliary battery charging meanwhile would be the best set up.