The Final Fantasy musical game will have more songs beyond the initial set of tracks.
http://www.nintendoworldreport.com/news/29003
Theatrhythm: Final Fantasy will feature downloadable songs, character designer Tetsuya Nomura confirmed in an interview with Famitsu.
It is not clear if the additional songs will be added to the rhythm game for free, but paid downloadable content will not arrive on 3DS until the spring. The game is set to be released in Japan on February 16, with a new demo showcasing some new songs coming in early February.