Once RBN 2.0 goes live you’ll need a copy of Rock Band 3 to enjoy it as previous versions go unsupported joining Rock Band Weekly as RB3-only.
You notice there’s no new Rock Band Network content after February 15th if you haven’t taken the consumer leap and bought Rock Band 3. The Rock Band Weekly spewing of new tracks hasn’t supported older RB games since October’s RB3 launch.