Why not? We know the lineup tends to mean that Sunday is the heavier of the 3 days. It still is this year. Eminem has headlined Sunday previously. Melvin Benn had this to say:

""There was never a pre-ordained plan that said we would have a rock day. It's what's around that's most suitable for us at that particular time. AC/DC would love to have played, but they have got commitments in the US at the same time. People who say, "it isnt very rock orientated" - certainly compared to previous years - will be right. However, you'll find that there will be some very special additions to the bill that will lay those concerns to rest!""