I've already acquired the pet from another guild, but it's still exciting that my fellow guildies can also purchase the pet now too. More pets for everyone!
Although we've unlocked the pet, we won't be opening up for collectors to join. In the end, we're still primarily a raiding guild, and even if I adore pets, it's not the main focus.
For those seeking the Thundering Serpent Hatchling, I still recommend taking a look at the guilds listed on the WarcraftPets forum thread. :)
Many thanks to my guildmates who were very dedicated in earning gold in all challenge modes (even if the goal wasn't to unlock the pet :P). Congrats to everyone in my guild, and happy collecting!