There's no real reason why they would suddenly put out a cease & desist now rather than when the first two cases were released; I'd rather have a more thoroughly checked, better game than a vague speculation on how Capcom will or will not react.
I'd rather see case 3 released when the voices are in and is generally complete, and then another patch for the entire game. Should not be illogical and also tide people over well (and allow for a massive final test on that case)
@Xdqwerty, Osu! Tatakae! Ouendan! is the Japanese version of the game, different settings/characters/songs but otherwise identical mechanics. I played that before I knew about Elite Beat Agents lol. Both fantastic games https://en.wikipedia.org/wiki/Osu!_Tatakae!_Ouendan