Also on the same Facebook page, the authors reveal that there will be a give-away of ARCs for Caliban's War closer to the release date. In the meantime, Orbit also have a sample of the novel available.
Update: Daniel Abraham has confirmed that Abaddon's Gate replaces the original working title for Book 3, Dandelion Sky:
"The consensus (probably accurately) was that Dandelion Sky was a little too pastoral and Ray Bradbury for the book as it is."It's worth noting an unfortunate similarity between the new title and Warhammer 40,000. The principal villain of WH40K, Abaddon the Despoiler, captured the Cadian Gate during a recent in-setting military campaign, leading to the two words cropping up a lot in those works. I doubt many people would confuse the two, but it's something the publishers might want to bear in mind.