A post over on the official Guild Wars 2 forums
has confirmed that a new Refer a Friend system will be making its way to the lands of Tyria, allowing up to three friends to be invited to play a free trial.
Details are still slim, but players who have an account in good standing that was created before 23:59 PST (5:59 PM AEST) on November 6 will be able to invite up to three friends on November 12 to travel in Tyria on November 15-18. The dates are actually coinciding with the upcoming free content upgrade called "The Lost Shores", so invited friends will be able to experience all the events as well.
We'll have more details on what the free trial will be restricted to as it becomes available.