Even if I could mentally stretch to believe that oasis are reforming next year it is another massive leap again to think they will do glasto in the first run.
They are only going to do it for the cash. Noel has said it. Glasto don't offer the big bucks. They will be tied into contracts for mega gigs first and then, maybe, if they don't end up disintegrating again, but probably not. They might play glasto.
It'll be just like when The Stone Roses reformed. Everyone expects beloved band to play beloved festival but it doesn't always work like that.