Harmonix recently made a few announcements at this year's CES, including that Rock Band 3 won't be arriving this year.
The main project for the studio this year will be the previously announced music title featuring songs from the Beetles. As for here and now, Harmonix also detailed the DLC features available for the Wii edition of Rock Band 2.
Since Nintendo has skimped out on a hard-drive, an SD card is the ideal route for storing those downloaded tunes. A single track averages out at around 24MB, and so the maximum sized card for Wii (2GB) can take on approximately 75. There are workarounds to access 4GB varieties, but on average Wii owners are looking at grabbing around 70-80 tunes per card.
The downloadable content is in the final testing stages and Harmonix is working as fast as possible to deliver the 20 free bonus songs for Rock Band 2, plus an additional 30 songs from the Rock Band DLC Catalog to fans as early in 2009 as possible.