Rock Band 4 released after a huge hiatus. In fact, we were pretty sure that Harmonix was done making games in the series. But one of the principles that they did seem to abide by when the games were at peak popularity was that the convenience of keeping a central library of songs for the series. It’s an important one; switching discs and losing our library of purchased DLC would diminish the experience. The company is continuing the practice through the newest game.
Now, players will be able to import songs from the very first Rock Band onto the new one. This is assuming they are still using the same platform and username that they used back when they first imported the Rock Band tracks to a subsequent game.
This import comes to us following the very recent update that allowed gamers to import Rock Band 3 songs over to the new title. Harmonix seems to be working at a pretty decent rate on this project, and the song library for Rock Band 4 is rapidly growing.
Source: IGN