Patch 3.3.3 will be bringing about some welcome changes in the user interface, instances, and those pesky frozen orbs you can never get rid of, but it looks like they aren't the only things getting an overhaul. Fishing around in the PTR files found some new models as well.
Two new mounts have been added to the game files, the Blazing Hippogryph and the Wooly White Rhino. Where these mounts are obtained is currently unknown -- we'll update with more information on the new mounts as we learn more.
In addition, it looks like Anduin Wrynn finally got his wish -- a new model has been added for the young king-in-training. With more and more models getting overhauls, does this mean players of male humans might finally get rid of that funky overbite? Check out the gallery for pictures of the new mounts and models, and stay tuned for more 3.3.3 PTR info as it develops!
Update: MMO-Champion is reporting that the two mounts are TCG rewards. However, with the recent developments between Blizzard and UDE, this information may change. Keep that in mind, and we'll let you know if we hear any word from the blues about it.