A double experience weekend will be in effect from Saturday, September 1 through Monday, September 3. It was announced on the forums:
Greetings intrepid gamers,
For the many of you asking the question, yes, we will be having a double XP weekend for this upcoming holiday. We have it scheduled from 12:01 AM Saturday until 11:59 PM Monday.
We hope you have a wonderful weekend!
Holly "Windstalker" Longdale