Because I keep seeing these questions pop-up, and because some of my previous answers have been lost to the forum monsters I’m going to post the info I currently have regarding the mount changes. This is how the mount changes work as I understand it, they may change before 1.12.1 goes live.

After 1.12.1 goes live there will only be one riding skill that will work with all mounts. The skill currently has 2 ranks Apprentice(75) and Journeyman(150).
# Apprentice(75) skill will be required for all superior(blue) level 40 mounts, the Rank 11 PVP mounts and the superior(blue) AQ40 mounts.

# Journeyman(150) skill will be required for all epic(purple) level 60 mounts, the AV faction reward mounts and the epic dropped mounts (Deathcharger, Raptor etc.).

# Warlocks and Paladins who complete their mount quests will be given Apprentice(75) and
# Journeyman(150) upon completion of the quests.

# All mounts will be bind on pickup and have a level requirement.

# Purchasing a non-racial mount will require exalted reputation with that faction.

When the patch goes live the following changes will take place:
# Characters who have a mount in their inventory(backpack or bank) will be granted the skill level necessary to use it.
Apprentice Riding Skill requires level 40 Journeyman Riding Skill requires level 60

# Players with the Rank 11 PVP mounts will be granted Journeyman(150) skill.

# Players with Riding skill but no mount will be granted Apprentice(75) skill.

# Paladins and Warlocks who have already completed their level 40 and level 60 mount quests will be granted Apprentice(75) and Journeyman(150) respectively.