Salthem, a moderator on the European PTR forums, has tried to ease player fields by offering some clarifications about the way guild banks work. First of all, players are not allowed to delete or transfer characters with guild leader status. When a new player is given the role of guild leader, they gain complete access to the stores of the bank. If a guild leader character is banned (which I can't imagine happens a lot, but it's possible), a GM can give leadership to somebody with the guild. If a guild is disbanded, the guild leader receives all the items in the mail.
So in the end, the guild leader is still quite capable of just dissolving the guild and taking all the loot, which isn't much of a change from the status quo. Still, it's nice that they finally provided clarification, because it's a problem that was generating a lot of unnecessary commentary.