You really get easily hyped by everything.

There's nothing exciting about trailers on Wii U. At most maybe we will see special trailers on Nintendo shop that have two video streams - one for main screen and second one for gamepad screen for example showing some diffrent aspect of the game or a gamer moves during gameplay parts.

Both of these. I'm all for Wii U, but Joe, you gotta cut it back. I'm to the point where I enter a thread with an interesting title, then see it was posted by Joe and think, "Oh, nevermind."

I agree with everyone else on the idea that it won't replace trailers, but I think OP has a nice idea. Nintendo NEVER do demos (unless you count a couple of Wiiware games).
I think there is a chance they may do something like this for a Mario/zelda/ metroid game as there are some people who need more then a trailer, it wouldn't be for frontline advertising but for the fans to build up excitement and get people talking

Advertisers are trying out new ideas, look at Portal 2 for example, Valve used some very interesting marketing to build excitement, sending out cryptic emails and the "potato sack" games, it did cause a little back lash but over all it worked very well.

If they are just using the same textures, engine etc that is in the game it won't take a huge time to create and will capture peoples interest, I think it will be more then just pan and view, it would be more interactive, but I can see fans LOVING it if it is done right, and they would download loads of data to get something cool.

The way it works is that if fans are KEPT interested they will talk about the game to anyone that will listen - so it spreads by word of mouth.

"Hey did you download the lastest RE:6 IAD? It was EPIC, can't wait for the game!"

I agree demos are better, but done RIGHT a interactive ad, that contains something cool or exciting could be very effective. If you can send it on, or even effect it in someway and send it on to your friends via the UWii it could go wonderfully viral....

"What are you guys talking about? It's really great, I'll send it to you, you'll see"

And using WiiU 24/7 it could be downloading before the friend even gets home, so no wait time, or if he is home it could download in the background. (really hope WiiU does this)

Personally I would love a Half-Life 3 Interactive Experience - hey a guy can dream

How about something that gave hints to  Portal 3 - half life cross over, or mini puzzles, or maybe  a treasure hunt that can be joined in with your friends or a combination of these elements?  I think interactivity using the WiiU controller  could be very cool combined with a very smooth painless online experience. 

Imagine multiplayer interactivity with voice chat, hearing your friends excited by finding clues  that tell you what possibly could of have happened to Cave and how chell came to be...revealing some more of the back story and hinting at what might be in the future...and if you complete the puzzles/ or discover the item you get a  companion cube mii.

In someway it would be more excitment building then a plain demo - esp. before the demo comes out.