SOMETHING will happen. I think 18 months is pushing it, but they will play some major gigs.
Don't know about worst kept secret... nothing's confirmed, nothing's actually known, so any officially arranged stuff still actually is a secret. EVERYTHING has been speculation, guess work and rumours. It's just that it's a pretty obvious thing for them to do so everyone's assuming it will happen.
18/12 Black Sabbath
14/1 Iced Earth
18/1 Lamb of God