MMO Champion has just published a preview of 3 MOP mounts
Grand Expedition Yak Mount Preview
Sold for 60000 gold in The Grummle Bazaar, a village located just outside of One Keg in Kun-Lai Summit. Reputation or Guide Discounts apply. The mount can hold up to 3 players, and has 2 vendors when you summon it : The first one can repair you gear, the second one is an Arcane Reforger.
Dragon Turtle Mount Preview
Pandaren Mounts will be sold at the Pandaren camps in Stormwind and Orgrimmar.
Normal version :
Epic version :
Water Strider Mount Preview
For the moment, only the Reins of the Azure Water Strider is sold in game by the Anglers faction. It requires Exalted reputation and costs 5,000 gold before discounts.
Images from MMO Champion