ArenaNet will be enabling the guesting feature for cross-server PvE on that date. When they do, the world transfers will no longer be free.
If you are transferring to join AIE on our home server, you can find us on Dragonbrand.
There is also an interesting restriction on guesting.
You’re eligible to guest on only 2 different worlds at a time. Each time you guest on a world, that world becomes one of your eligible guest worlds for the next 24 hours. After 24 hours, you may choose to guest on a different world. You may log in to any world you are eligible to guest on as many times as you wish with no restriction.
While this doesn’t look like something that will cause any significant problems, it does mean that the guesting system is not as lightweight as many of us expected.