The bad news? Activision is making Guitar Hero: Aerosmith. Wait, that's not the bad news. The actual bad news was that all those Guitar Hero III tracks you downloaded from either Xbox Live or the PlayStation Store won't work on your copy of Guitar Hero: Aerosmith.
Here's a dash of good. Guitar Hero World Tour will support your existing GH III downloads, which begs the question "Why would you buy Guitar Hero: Aerosmith?"