I heard that Cataclysm is going to be a ground-breaking change to world of warcraft. Is blizzard planning to change what level you can get your apprentice riding skill?
No, Blizzard is not changing what levels you get mounts. The levels are still:
Level 20 - 60% Mount
Level 40 - 100% Mount
Level 60 - 60% Flying Mount. Allows you to fly in Outlands and "Old World"
Level 70 - Fast Flying. Costs 5000g (rep discounts available
Level 77 - Cold Weather flight. Costs 1000g. Available at 68 with the Tome of Cold Weather Flight
They are also letting you buy the 310% speed for your mounts if you do not already have a mount that goes that fast.