Here is the expansion timeline as I've found it. I'm looking for confirmation that this is the correct order:

Dark Age
Fire for Effect
Death from Above
Dropship
Liao Incursion
Counterassault
Falcons Prey
Age of Destruction
Firepower
Annihilation
Domination
Battleforce
Vanguard

Technically, yes, thats right in order of release, but the dropship is more floater, it doesn't really fit into the timeline. And Battle force is an on-going WizKids Gimick to promote Faction-pure-ness in a Gunslinger dominated world. They'll be releasing more as time goes by.