Karaoke Revolution Vol. 2 was fun, but it didn't really add much to the original experience. The quantity of recycled artwork was disappointing, and the new Medley mode was less than seamless.
Konami today announced Karaoke Revolution Vol. 3, which has yet another 35 songs, but also duet play. While this will certainly drive up sales of microphones to gamers to thought they needed only one, I think it will also significantly increase the game's party value. If they recycle the artwork once again, I'll expect a more reasonable price tag ($30). But I'll probably be suckered into another volume of this sing-along game regardless.
Karaoke Revolution for Xbox was also announced, and will support downloadable content.