Rock Band, Rock Band Reloaded and Rock Band Reloaded for iPad, will be delisted from the App Store. After this date, the games will be gone and users will no longer be able to purchase any DLC.
Earlier this year, Rock Band app users received a message saying that the app would be pulled on May 31. At the time, EA stated that the message had been "sent in error." There doesn't appear to be a mistake this time around, as the iTunes pages for each app confirm the delisting. The original error, apparently, was that the message was sent two months early.
Update: EA has posted a Q&A regarding the delisting, stating that "EA's licensing agreement with Harmonix is ending and as a result, EA is discontinuing downloads of Rock Band iOS and Rock Band Reloaded iOS on the App Store after July 31. "