We have a sequel... a Japanese sequel that never came to America. The game went through heavy dubbing as it got ported to American consoles. I would imagine that it was insanely expensive to dub as you had to license songs, completely redo the graphics and stories, and basically redo how you play the songs. I would imagine that they did not get as much money as they wanted, so they did not port the sequel.
I personally love this game. I picked it up for $3 about a year ago, and I just now completed Jumping Jack Flash on Divas. I recommend this to all DS owners right behind my personal favorite DS game (TWEWY). The songs are all very fun to listen to (this game helped me discover Good Charlotte) and it is unique and fun to play. Go to your local gamestop and pick this one up from the bargain bin! If you like good music and good musical games, you won't regret it.