It might not have set US cash registers on fire and is yet to be released in Europe but this hasn't stopped a sequel being announced for Japan. Dengeki Online reports that during a Nintendo retail conference in Japan it was confirmed that Moero! Nekketsu Rhythm Damashii Osu! Tatakae! Ouendan 2 is heading to the Nintendo DS.
Given that we're still waiting for the release of Elite Beat Agents in Europe, it's probably not a great idea to hold your breath for the sequel - you might pass out.