The press event information included that the pandaren racial mount will be cloud serpents. No images were released, but we're likely to see them from the beta sometime.

Yak mounts will also be available in Pandaria, but they aren't the racial mount.

Cloud serpents aren't a racial mount, they're a mount available through daily quests for everyone. I saw information that it would be some type of turtle but I don't have a link handy.

@NatalaH: You're right. I misread. The cloudd serpent mount will be a reward from the "Order of the Cloud Serpent" faction, which are pandaren, but not the racial one.

http://wow.joystiq.com/2012/03/19/mists-of-pandaria-zones-and-questing/
"the Jade Forest is home to the Order of the Cloud Serpent, a faction of pandaren that raises and trains, well, cloud serpents. These beautiful, Chinese-style dragons exhale cloud breath (the effect reminded me a LOT of Wind Waker, in a good way), and the Order is more than happy to train you to ride one -- provided, of course, that you can pass their tests. The process starts with an egg that can be hatched with a series of quests, and then dailies allow you to feed and train your newly hatched cloud serpent until the day it can learn to fly. Once you prove yourself on the racetracks and skyways of the Order, the serpent is yours to keep as a mount."

@Shinae

My thoughts exactly. That leaves us either the yak or a NYI mount.

The Panda racial mount will be a dragon turtle. It was confirmed by GC. What they look like, head over to mmo champion, they did some digging for the models.

@Shinae

So it's Wintersaber and Netherwing combined then? As long as the races don't involve throwing stuff at us, I can live with this.

Durandal's right I looked it up:
http://www.mmo-champion.com/threads/1101499-Turtle-Dragon-mount