Before the Fall will be coming in 3 parts. Part 1 looks to have most of the new dungeons and story content and is coming January 20th, Part 2 will finish off the main story leading up the Heavensward and be hitting in late March, Then Gold Saucer will be its own update between the others in late February.
The Dungeons coming in 2.5:
source: The Loadstone
Anybody else going to be on for the Imperial Operation tonight?