Right at the tail end of its Digital Event today, Nintendo sneakily announced Mario Party 10 for Wii U while talking about games that are compatible with its new line of Amiibo figurines.
While no release date was given, Nintendo did release a trailer for the game showing off the all-new Bowser Party mode, in which one player (using the GamePad) battles against the four other players. The game will also include traditional Mario Party style minigames as well, and will be compatible with the Amiibo figures, though Nintendo did not elaborate on how that will work.
Mario Party 10 will release sometime in 2015.
Source: Nintendo