Blizzard has released two previews of the upcoming Operation Gnomeregan which sets Alliance players in a series of quests to retake the Gnomish capital. Apparently, Mekgineer Sicco Thermaplugg is still alive. The one we defeated in the dungeon was not him, but a construct posing as him.

Vol’jin and his Darkspear trolls have learned Zalazane had used dark magic to fake his death. Zalazane’s severed head, the one adventurers brought to Sen’jin Village, reverted shortly after into its true form … a colored rock Volunteers shall side with the Darkspears to retake the Echo Isles from its mad ruler.

Blizzard Quote:
High Tinker Mekkatorque, betrayed by Mekgineer Thermaplugg and forced to flee the irradiated city of Gnomeregan with the few of his fellow gnomes who managed to survive, is preparing to reclaim his once glorious city. Meanwhile, in distant Durotar, Vol’jin of the Darkspear trolls is determined to exact revenge upon the witch doctor Zalazane for dividing the Darkspears and seizing the land bestowed to them by Thrall: the Echo Isles. Read more about the ongoing struggles of the gnomes and the trolls… and their plans to seek redemption.