Since it's looking hopeful that patch 2.3 will be released within the next couple of weeks, it's probably time to start getting prepared for all the long-awaited features that are being added to the live realms. Aside from Zul'Aman, guild banks are probably the biggest new item coming out with the patch.
While guild leaders will undoubtedly be delighted to delete their bank alts, (some of the guilds I've been in have had as many as five or six,) and will also have to make difficult decisions about which members get access to the loot, I'd like to focus more on the impact upon individual players rather than whole guilds. Most players that have been in Azeroth for awhile probably have a bank alt that's mainly used to store trade goods and sell things on the auction house. In 2.3, according to all reports thus far, it should be possible to set up a one-alt guild so that your bank alt will have access to much more storage space.