MB Inc is a side-company of Nintendo and Fantendo. It helps them produce games.
So far, MB Inc. has only produced one game, Mario Kart: Speed Legends, although many more are in the making. There are rumours that they will be making a sequel to Luigi's Mansion: Dark Moon and Donkey Kong Country Returns. Furthermore, they have announced a new Mario platformer for the 3DS and the Wii U (probably not in the Super Mario Bros. series) and will be making 2 3D mario games, one of them being a sequel to Super Mario 64. Lastly, they are going to be making a sequel to Wii Sports Resort.
They are deciding wether or not they will make a Mario Party game or a Mario Sports game.