Hey everyone, there's a demo for the game at any Best Buy location that offers demos! I've been seeing rumors of it on various places, such as reddit and gamefaqs forum. I went today, and I got to play the demo too!
The demo has all the starting characters, 4 Bowser Minigames, and 4 normal Mario party minigames.
I can supply picture proof that I played the demo, if I need to--I was kinda skeptical about it until I went, since there really hasn't been news about it.