Harmonix specifically saying they have plans for the next three months (in the past they've said six) and that they would tell us more about the future of DLC towards the end of those three months. Henry's tone was somewhat pessimistic in the same thread and he said something along the lines of "I'm sorry, it is not a very good day for Rock Band announcements". DLC is still coming to an end. This pack probably began its planning stage before Harmonix knew that.
Edit P.S.: Think of it this way, it was a miracle we were able to get Aerosmith before this ship sank.











