CVG have brought to light a /achievement command in the alpha of WotLK suspect much like LotRO & WAR's.
More information.The achievement system can be accessed by typing in '/achievement' into the Wrath of the Lich King Alpha test, according to blog Death Knight, who also took the screenshots you can see below.
The images seemingly reveal that players will gain achievement points for doing a variety of tasks that range from completing 2000 quests to exploring the whole of Azeroth.