It's been about five months since the release of Rock Band 4 and it is finally getting an online multiplayer mode, something that the fans has been asking for for a long time.
Harmonix has been talking about adding an online multiplayer mode for a while, and now they are finally enabling friends and strangers to live the dream of being the best online rock band in the world. Seems like they found the time to make multiplayer now that their plans of a PC version failed.
The new mode is currently called "Synchronous online multiplayer" and will be sort of like "Quickplay, modified to provide a fair and streamlined experience for console friends looking to play Rock Band 4 together online". Harmonix will also implement a better way to pick songs in online multiplayer, making it so that not just one troll keeps picking random songs.
They have also created a "secret sauce" to make the online multiplayer even better than in previous games. According to Harmonix it will eliminate most of the problems the earlier games had.
This is all part of a big update coming later this fall. The update will be really big and bring a lot of new features, it will even be bigger than the One Direction DLC "We’ve got brand new features heading to Rock Band 4 that have never been in any previous Rock Band title, ever."
Source: Harmonix