Tsunoda's answer: Look at Dance Central. Said Tsunoda, "Dance Central is already incorporating a lot more than two players," adding that "it's not necessarily any kind of limitation as much as it is developers just trying to customize the experiences around what they think is the best way to play." Furthermore, Tsunoda noted that it can be difficult to work loads of players into a game's design, but reiterated that Dance Central is "already incorporating more than two."
Not satisfied, we contacted Harmonix for further clarification on this issue. Read the response after the break.