Moving server - account question
If you transfer, your regular bank and items in your inventory transfer with you but your guild bank and any items or gold in it do not. It remains on that server and will be inaccessible to you, even if you guest there. So before you transfer you need to clean out the guild bank. After you transfer, my understanding is you will need to recreate the guild bank from scratch as all influence and upgrades will be on the old server.
When you transfer to another server, your account wallet and anything else account-bound moves with you, such as your bank and all items in it. Soul-bound things move with the characters, as well.
Guild banks, on the other hand, are tied to servers, and will not move. Once you leave the server a Guild bank is on, you can no longer access that Guild bank, nor will guesting allow you to access it.
Thus, if you transfer, make sure to take everything out of the Guild bank, and be aware you will lose all upgrades and influence.
ArenaNet Communications Manager
Basically the question is – is there any way at all that a guild bank can move servers with you?
In a nutshell, as explained above, no. The guild bank will stay on the world on which it was created.
Communications Manager
Guild & Fansite Relations; In-Game Events
ArenaNet