There have been a lot of reports on the massive changes to the talent trees in Mists of Pandaria, but I haven't seen one place where everything is documented on how the new trees work. How have they changed from the current version, and what features have been added to make them better?
All of the new talent specs are on Battle.net and have been for months, now. Basically, talents have been changed from trees to tiers. Since Blizzard saw that most players chose the same talent points for particular specs, they turned most of those talents into base attributes of the class and specialization.
The current talents are primarily skills. From each tier, you can only choose one. And Blizzard has stated that you will be able to change talents easier, including no longer having to reassemble an entire talent tree whenever you respec.
Please note, as on the linked page:
All specs, spells and talents are not final and may change during the development process.
Here's how the new talent system is structurally different.
At level 10, you choose a specialization. Abilities are immediately granted based on this choice. More abilities are also granted automatically as you level based on this choice.
Every 15 levels (15, 30, 45, 60, 75, 90), you will choose between 3 abilities (talents)... getting one and locking out 2 others. The three available choices at a given tier are in no way restricted by your specialization choice or by your prior talent choices.
The choices can be thematically similiar to the specialization choice (for example, mage level 30 talents are arcane, fire or frost). The choices can completely ignore specializations choice (for example, mage level 45 talents are all frost related).
TLDR: No more talent points. You choose a specialization and 6 talents by level 90. 7 choices in all.