Patch 5.4.7 was released today and changes include a new addition to the Pet Journal and 15 updated abilities.
The Dread Hatchling was officially added to the journal, but we'll have to wait a while longer before collecting it. Players that purchase the WoD CE or the Digital Deluxe will receive the pet once the expansion is released (or a little sooner - just keep an eye on your mailbox).
The pet is quite adorable, and you can check out its idle animations in the Pet Journal preview window. It does a cute little hop and then proceeds to squawk or cheep a few times. If only we could zoom in a little more to see the preview better lol. :P
Developer Jonathan LeCraft called for feedback on some of the more disliked/least effective pet abilities a while ago, and it looks like adjustments based one some of that feedback went live. The majority of changes involve damage/healing/hit chance values being tweaked slightly. A list of all the abilities that were updated can be found here. Changes weren't noted though, so if you're curious about what was altered you'll have to find an older version of said ability to compare.
EDIT: A more detailed list of the ability changes can be found here.
As with all patches, the potential for bugs is there. Some players may find that a few pets have gone missing post-patch (specifically RAF and Blizzard Store pets), but this should be resolved after a realm restart. I'm guessing they will roll out restarts late tonight; check your Pet Journal again tomorrow. We'll see if missing pets are returned or if it's an ongoing bug.
UPDATE: More information on missing pets and mounts here.