Later this year (Holiday 2016) developer Harmonix will be bringing synchronous online multiplayer to Rock Band 4.
This major feature has been in development since before Rock Band 4 shipped last fall, and while it won’t be out until later this year, Harmonix promises more information at E3. They will also be continuing to fix the back end for those whose DLC libraries don’t match and want a quick and easy process for choosing songs as a band.
The fall expansion pack will also be receiving more information at E3 this year, which takes place from June 13-16. You can check out the trailer for the upcoming multiplayer feature below: