I think the thing is that they've headlined other festivals, slightly smaller than glastonbury. They're similar to Arcade Fire for example, who weren't quite big enough after The Suburbs, however still headlined a load of other festivals. After Reflektor they were just about big enough, and the album wasn't massive but it was big enough to propel them to headline a festival like glastonbury. I think they could do it, they just need 1 more album to make them a relevant band again. Doesn't even need to be massive, just not a flop.