We’re currently working on the implementation of a system in patch 4.2 which will handle the removal of the Keyring, while causing you as little hassle with keys as possible. Some keys which no longer serve a purpose in the game will automatically be removed from your inventory. In return, you’ll be compensated for them with their respective vendor sell prices in gold. You might also have random leftover quest keys from outdated quests, or quests which were removed in Cataclysm. Keys that fall into this category have no use and no sell price, as they are labeled as quest items, and will be automatically removed from your inventory. Any remaining keys that might still potentially serve some use in the game will be transferred into your regular inventory. If there is not enough space in your inventory to hold any leftover keys once patch 4.2 hits live realms, the keys will be placed in a backlogged storage system. Once space is made for a backlogged key, the key will take that space after you log out or switch to a new zone (i.e. changing continents, entering a dungeon or Battleground, etc.).
We are continuing to work on new ways of allowing you to better manage the storage of various items in the game, and it is our goal to make sure the removal of the Keyring causes as little inconvenience to you as possible.