I haven't confirmed this myself with the device yet, but it looks like from my sources that the Wii U browser will support most or all of the HTML5 features, and suppose to be based on the webkit base.
I think it would be a great opportunity for us to make companion apps for games released on the Wii U, plus apps for the TVii features too. The web browser can be accessed and used anytime on the tablet controller itself, while playing a game or watching a show or movie.
The controller screen resolution is 854x480. http://en.wikipedia.org/wiki/Wii_U_GamePad
With some of the tests I have done with the community mfa examples into html5 demos on desktop and android, I think our creations on Wii U will be another selling point. Now if we can get our hands on one to test out, and see if the browser has hardware browser support.
I also wanted to bring up that there are some app stores that sell HTML5 apps for Android, desktop, and iOS devices. So that is another avenue we check out.
Very big thanks to Clickteam all of these years, and to the awesome Community who is always super helpful and nice. We all help each other make our dreams come true and knowledge grow!