Although ArenaNet called their third closed beta a final one, it seems now that tonight will be the real final one.
The announcement was made only on Facebook. This brief stress test will take place on August 2nd from noon pm to 4pm EST, which means to us Europeans(GMT+2): Today Thursday 2nd of August 2012 at 9pm until 1am Friday. It’s uncertain whether players will be able to play characters from previous beta events or whether they will need to create new characters.
What they want to stress test is the server capacity (they brought down the total amount of servers and worlds) to make the World versus World PvP and generally the game experience better with having more players on each server. Also they want to test the World versus World player selecting, ranking and other fine tuning. They will be actively fine tuning the game further during this short event, including difficulty, which means that you can expect to see a lot of connectivity problems or server restarts.
The game will be released officially on the 28th of August 2012, with early access at 25th of August 2012 (Sat 25th Aug, 09:00 CEST) for those who have pre-ordered a digital edition or 27th of August 2012 for those who have pre-ordered at a retail store.