Eberron? Count me in!
I would rather WOTC give us a new campaign world. If I'm not mistaken, the most recent one was Eberron in 2003. That's 15 years since we got something fresh.
Between this and Keith Baker saying he was under a deadline for a big project, I can only hope.
I really do believe it's likely the two settings will be Spelljammer and Eberron.
I agree, assuming this isn't all a cruel joke, except I think it will be Eberron and Planejammer (merged plan escape/spelljammer setting).