It’s a big week in the world of Rock Band as game developer Harmonix announced today that Rock Band song downloads have surpassed 6 million and counting. Compare that to the 2.5 million hits the game was reporting in mid-January, and you get a sense of the runaway downloadable-content train that is Rock Band. This news comes in the days leading up to the game’s latest patch, which will include a shiny new song storefront with full in-game integration. Yes, folks, this means no more heading back to the dashboard in order to get new tunes; instead, you’ll be able to do it from inside the game, as well as take advantage of the new ways to browse through songs: by artist, genre, difficulty and year of release. Each song listing will now also indicate the difficulty rating for each band member, as well as a preview of the song.

The success of Rock Band’s downloadable content is partially due to the game’s popularity, but is also in part because of how fresh the Harmonix team keeps the game by consistently adding new songs. Granted, the ability to do so might go hand-in-hand with the nature of the game. However, with episodic content rumored for GTAIV and already rolling out for Mass Effect, we can only hope that DLC will become an integral part of how all games are made in the future and how we experience them and the worlds in which they exist.

As for how this new integration will affect the sales of Rock Band DLC, there is no official word from Harmonix on how they think the numbers will fair. It seems clear to me that they’ve got nowhere to go but up.