The first Wii game likely to ship with a peripheral in the US (not counting foam doodads) is not a Nintendo first party game. It is a licensed game. From Disney. Based on a made-for-TV movie.
Disney Interactive is bringing an adaptation of their hit movie High School Musical to the Wii as a karaoke game. The story of the game will follow the first movie, while also affording players the chance to sing the songs from the second. We weren't really aware karaoke games needed or could support stories, but we'll accept it. High School Musical is set to ship this August with an included microphone.
High School Musical is facing competition only from Dance Dance Revolution: Hottest Party in the race to be the first US-released Wii game with a special controller as well as the first full music game for the system. That's pretty progressive for Disney!