Blizzard has already begun to release information and previews of the next large content patch, 4.2. Within the latest updates, they announced that upon completion of a new legendary staff, the entire guild will be awarded with a non-combat pet.
"Those who complete the staff won’t be the only ones to receive a reward, though. As this task requires the dedication of an entire guild, upon completion of the staff all guild members will receive a unique non-combat pet to call their own."
A Different Direction
This is definitely a new and unique direction for vanity pets. Unlike the current guild achievements, where some guild participation is only moderately necessary, this new "legendary" companion may absolutely require not only guild participation but a guild raid as well. We will have to wait and see to hear more details about how this legendary staff and companion pet are obtained.
4.2 Preview: A "Legendary" Pet
April 28, 2011