None of the bands touring this year from Splendour time onwards are likely to come back.
AC/DC are fucking boring, and they'd be worse as old men. Heaps of people like them though, so they'd be a good headliner, particularly because of the over 18's bogan factor if they want to draw adults. Adults = drinkers = extra money. Don't you think they'd do an arena tour though for such a huge comeback? We'd know if there was a planned comeback by now.
R.A.T.M aren't very likely.
Interpol and QOTSA are, so are Kings of Leon and White Stripes. The former two would make it too similar to 06 though.
I'm pretty sceptical about that no under 18's thing. I'm gonna look into it. Under 18's have been the driving force behind the increased popularity of festivals in the last 4 or so years. Seriously, Homebake didn't sell out until two weeks before it was held in 03. Anyway, most of us on Bored of Studies should be 18 by then, so who cares?