Well AC/DC, The Police and Bon Jovi will certainly not be performing at Rock im Park in 2008. AC/DC would have been cool.
There are a few more rumors though based off of bands announcing they will be playing European Festivals next summer. The rumors are:
Judas Priest
Radiohead
Muse
Alterbridge
Sum 41
Van Halen
Bruce Springsteen
Slipknot
Mudvayne
Disturbed
International Noise Conspiracy
Serj Tankien (Solo performance by singer of System of A Down)
NOFX
If these rumors are confirmed they will be added to the bands allready performing below:
Metallica
Motorhead
Babyshambles
Bullet For My Valentine
Die Toten Hosen
Dimmu Borgir
In Flames
Nightwish
Rage Against The Machine
Sportfreunde Stiller
The Hellacopters