That video can't be a real Mario game! Here's the reasoning why:
The video is too advanced in the cel-shaded graphics to be made for GameBoy Advance. GameBoy Advance doesn't have the proccessing power to pull off full-motion, brightly colored games like the one shown in that video.
Also, if you look at the GameBoy Advance logo at the beginning of the video, you will notice that the logo spins off into the distance as the game starts. The GameBoy Advance logo does NOT spin off into the distance when you play any other GameBoy Advance games...
The quality of the graphics do look appealing, but I'm pretty sure this is just a hack.
If it is a true Mario game made by Nintendo, then why didn't Nintendo announce it at the E3 Expo?