SAN FRANCISCO—On Wednesday, two months after the Rock Band game franchise sputtered back to life, the staff at music-game developer Harmonix confirmed to Ars Technica that an even bigger release is on its way. Rock Band 4 is coming, and according to Harmonix, it'll launch on Playstation 4 and Xbox One by the end of 2015. However, it wasn't quite the announcement event we were hoping for.