I have a feeling Testament may be one of those bands. I cant see the Big 4 happening without them being the last 4 bands on the main stages. I cant see linkin Park or offspring relagated to afternoon slots on the main stage, weirder things have happened though.
So Yeah I have a gut feeling Testament will be one of the big metal bands he is talking about.
Why can't Megadeth and Slayer play on the metal stage? Slayer headlined the metal stage two years ago. That was followed by Iron Maiden on the main stage. Also the amount of standing room at the metal stages should be enough to accommodate the fans of those bands (at least there was in Brisbane).
Most metal fans wouldn't be too impressed with watching bands like Blink 182, Linkin Park and Offspring on the main stage. Perhaps AJ doesn't want to alienate one of the core demographics of his festival and will give them what they want on the metal stage while those bands are playing?
The first announcement suggest's he aiming more for the casual music fan with his choice of headline acts. My belief is that the second announcement will cater more for the core metal and punk fans.
I could be wrong about the Big 4. But I wouldn't rule out the possibility just on the basis of what stage they can play on. Of course there's that little voice in my head that's telling me if the Big 4 were to be included, it would have happened in the first announcement. But stranger things have happened.