On August 31st, ArenaNet will do a stress test for PoF. Starting at 10 PM UK (11 PM CEST), you will be able to play the demo again with a possibility to also test the elite specialisations.
Quote from the forum:
"We will be conducting a brief stress test for Guild Wars 2: Path of Fire on Thursday, August 31st, beginning at 2:00 PM Pacific time (-7 GMT). Anyone with a Guild Wars 2 account is welcome to participate. To join the stress test, please log in to your Guild Wars 2 game account, create a new “Demo” character on the character selection screen, and head into the Crystal Oasis. Play as you normally would play, but because this is a stress test, be prepared for possible in-game performance issues as the testing takes place. Thanks for your help!"