Doubt it. I expect their VGX thing to be something quirky like a real life super smash bros. match with people cosplaying the characters.
Lets say they do show it.. do you think Wii-U Would get attention and better sales
First off, it's not happening.
In some alternate world if it did though, they'd use the same tech as streaming to two gamepads so that the VR headset could be 3D. However this would take a lot of additional processing power. Devs supporting this feature would make the game run at gamepad resolution and have the TV just display the left eye's upscaled image. It would be cool since non players could still watch the game.
Support would be very bad though. Most games that support it would be sp games that work fine with off tv play. Devs would probably have to build the game twice though, similar to Uncharted 3. Naughty Dog built a 2D game and a 3D game. Wii U devs would have to build the standard 2D game and the 3D vr game. Not going to be worth it for the few 3rd parties still making Nintendo games, and I doubt first party games will support it unless they are built from the ground up for the experience.
You also need to think about the competition. Oculus rift is out there for PC guys and 9/10 times would offer the better experience with HD graphics and 60fps. I am not saying Sony is or isn't making their own VR headset for PS4, but in this alternate universe that Nintendo did it let's assume Sony did it too. That'd really steal thunder from Nintendo since casuals would just buy the Sony headset for the system they already own instead of paying $500 for the wii u plus headset.
So even if they did do it, I'd think it'd be a very silly move.