First off, Luigi is indeed in the game. You can find some footage of Mario’s brother in action at the 6:20 mark.
Next, a feature of the Tanooki Suit has been confirmed. Like in Super Mario Bros. 3, you can turn into a statue when you’re wearing the suit. Enemies will be unable to attack you in this state. Skip to the two-minute-mark for the footage.
This video also shows Tanooki tails on Thwomps and Boos, StreetPass functionality in action, a portion of a Bowser fight, another look at the Boomerang Suit, and more.