This is Game has a terrific write up of the fourth closed beta event for ArcheAge. The dev team has committed itself to over three months of closed beta testing in order to ensure that the most bug-free version of the game is released in its time.
Closed beta event #4 featured several key features that were not present in earlier versions: A new continent, a new race, three new regions, four 'seas', new monster and character animations and improvements to one of the existing races.
During CBT4, the dev team brought in new features and areas as well. For instance, the "footprint" system was deployed during CBT4. The footprint system is a way for robbed players to track thieves who leave a footprint as evidence of their action. The team also released the fortification and warfare systems, new quests and the auction house.
All of this is in preparation for CBT5 which will see improvements in the launch client and in player housing.
Read the full report at This is Game.