I could do without Clapton. Saw him a few years ago and he obviously did not give a shit. Definitely going through the motions. He's been pretty open in interviews about how much he hates the road these days.
I may be in the minority here, but I think the most likely legacy headliner next year is U2. They're working on a double LP, planning a new tour, have expressed interest in American festivals and are on AC's wishlist.