The Mirror isn't the source though. Someone else was. They're just passing it on.
It had already been speculated about two months ago that Led Zep and Metallica would headline Bonnaroo though, and Bonnaroo came out and said 'no', so I agree it's unlikely.
29/5 Dylan Moran
3-6/6 Sweden Rock Festival
19-21/6 Graspop Metal Meeting