No. It's not just the controller. It's a whole full-fledged new console with a new controller to boot.
Launches: 2012Games announced: Smash Brothers, Battlefield 3, Batman: Arkham City, Assassin's Creed, Ghost Recon Online, Darksiders II, Dirt, Aliens: Colonial Marines, Metro: Last Light, Tekken, Ninja Gaiden 3, FIFA 12, Madden 12, Driver, Lego City Stories
Size: Approximately 1.8 inches tall, 6.8 inches wide and 10.5 inches long.
New Controller: The new controller incorporates a 6.2-inch, 16:9 touch screen and traditional button controls, including two analog Circle Pads. This combination removes the traditional barriers between games, players and the TV by creating a second window into the video game world. The rechargeable controller includes a Power button, Home button, +Control Pad, A/B/X/Y buttons, L/R buttons and ZL/ZR buttons. It includes a built-in accelerometer and gyroscope, rumble feature, camera, a microphone, stereo speakers, a sensor strip and a stylus.
Other Controls: Up to four Wii Remote™ (or Wii Remote Plus) controllers can be connected at once. The new console supports all Wii™ controllers and input devices, including the Nunchuk™ controller, Classic Controller™, Classic Controller Pro™ and Wii Balance Board™.
Media: A single self-loading media bay will play 12-centimeter proprietary high-density optical discs for the new console, as well as 12-centimeter Wii optical discs.
Video Output: Supports 1080p, 1080i, 720p, 480p and 480i. Compatible cables include HDMI, component, S-video and composite.
Audio Output: Uses AV Multi Out connector. Six-channel PCM linear output through HDMI.
Storage: The console will have internal flash memory, as well as the option to expand its memory using either an SD memory card or an external USB hard disk drive.
CPU: IBM Power®-based multi-core microprocessor.
Other: Four USB 2.0 connector slots are included. The new console is backward compatible with Wii games and Wii accessories.
(Taken from the Nintendo E3 2011 Press Release)
Other facts: (GTTV interview with Reggie, thanks to hiero and others)
- The price point of the system will be competitive to the current prices of the PS3, 360 in terms of value
- The games shown for Wii U at the show were actually PS3 and 360 versions but the Wii U will look the same or better
- No BluRay Support
- Controller's screen is single-touch
- Backwards compatible with the Wii's Games, but no upscaling is done
- Nintendo Online system to be announced by the end of the week
Console + controller:  http://blogs.reuters.com/mediafile/f...ndo-wii-e3.png
Console:  http://i.imgur.com/eaN3V.jpg
Controller:  http://i.imgur.com/2Ski1.jpg  http://i.imgur.com/sf7fp.jpg
E3 Tech Demo:  YouTube - ‪Wii U E3 Tech Demo [HD]‬‏ (Stream quality)
Controller trailer:  YouTube - ‪Nintendo Wii U - E3 2011: Announcement Trailer‬‏
Copied from a discussion on reddit:
New Nintendo console: Wii U - Fact Sheet : gaming