I registered for tickets again for the next festival in June 2014 and did a quick google to see if there were any rumours yet because they were pretty bang on for this year and Michael Eavis (the organiser/owner) has said that all 3 headline acts have been booked and one is 'at least on par with the stones' so there's been a lot of speculation.

The biggest rumours for the headline acts right now are;
Kasabian,
The Foo Fighters,
Led Zepplin,
Pink Floyd,
Fleetwood Mac.
Noel Gallagher/Oasis/High Flying Birds.

(Various online sources including NME, Digital Spy).

If Pink Floyd/Fleetwood Mac/Oasis headline on one of the nights that'd be something pretty special!
Can't wait to try and get tickets in October, fingers crossed!!