The World of Warcraft: Cataclysm expansion is steadfastly approaching, but if you can't wait for release then details from the beta are spilling out every single day. Case in point the latest patch, 12539, which hasn't been officially detailed, but each of the changes is being picked up by the community.
The biggest change included with this patch is the implementation of the all new talent trees. If you're interested in the new skills each class will receive you should check out the latest talent calculators from MMO Champion.
If you didn't know about Cataclysm's Talent Tree update, then here's there plans:
"Our plan is to update all of the talent trees, in some cases dramatically, as well as add new talents where appropriate. We don’t plan to make the individual talent trees go deeper than 51 points, because we want to provide players more flexibility to pick up some talents in other trees. Instead, we’re introducing a new form of alternate character progression that we’re calling the path system. The idea is similar to talents, but rather than earning points on a per-level basis, players will earn points to assign by completing quests, defeating certain raid encounters, and completing other objectives in the game. Paths will be shared among multiple classes and themed around the Titans, creators of Azeroth, such as Aman’Thul, Aggramar, or Khaz’goroth (among others)."
There are also some other interesting changes in the patch, including paladin's Holy Power being implemented, as well as warriors acquiring their own version of consecrate. For all of the class changes that have been found so far make sure to visit Nihilum's patch notes, which are updated as changes are found.
World of Warcraft: Cataclysm is being targeted for release in 2010 for the PC and Mac.