Well the poster is fake for sure.
But I'll bet anyone $50 that the following are certainties:
Blink 182. Arcade Fire. Paramore.
GUNS N ROSES.
Guns N Roses have to be playing, they're the only band that fits the description from Melvin Benn (the festival organiser) that "one of our headliners are bigger than Jay-Z".
E-Festivals website has had the headliners bang on for the last 2 years, they knew Metallica, RAGE, and Killers were headlining 2008 long before the announcement. They added Radiohead late on last year.
They know- they have sources within the business.
I've gotta go if GNR play!!