I've lost count of the amount of times bands have said they're not playing Glastonbury, to then play it.
Up until 6 weeks before this year, Metallica 100% weren't playing. They were exclusive to Sonisphere. But that soon changed.
Springsteen's management turned it down in 2009, until he was contacted personally by Eavis etc to describe how much great work Glastonbury does for charity.
I don't really understand why the band would turn down the festival circuit. If it's ALL about money via Arena gigs, then that's disappointing - they don't need the cash.
To headline the greatest arts festival in the World would be a real coup, even for a band of their standing. They should speak to all the others who have done it and whose careers continued apace afterwards.