Another change coming with the Cataclysm expansion is a change in the way Dispel Game Mechanics work. Blizzard wants dispelling to be a little less trivial in PvP and also spread the dispelling capabilities amongst the Healing Classes more equally. They are raising the mana cost of dispel abilities as well as making them castable regardless if the target can be dispelled or not. They are removing Cleansing Totem, Abolish Disease, and Abolish Poison from the game altogether.

As previously mentioned, we are providing three dispel capabilities to all healing classes as follows:

Druids will be able to dispel defensive magic, curses, and poison.
Paladins will be able to dispel defensive magic, diseases, and poison.
Priests will be able to dispel defensive magic, offensive magic, and disease.
Shaman will be able to dispel defensive magic, offensive magic, and curses.

There is some trade-off that is being made in making these changes and we wanted to expand on this further.

Protection and Retribution paladins will lose their current ability to dispel magic.
All shaman will lose dispel disease and dispel poison in exchange for Restoration gaining dispel magic.
Restoration shaman, Restoration druids, and Holy paladins will need to talent into their defensive magic dispels.
Shadow priests wont be able to remove disease in Shadowform.
Mage, hunter, and warlock will retain their current dispel mechanics.
Body and Soul remains the same, and basically any dispel mechanic not mentioned above is currently planned to remain as it is.
When possible, wed like to combine dispels into a single action. For example, the druid ability to dispel curses and poisons might be a single spell with a Restoration talent that also allows it to dispel magic. This part of the design isnt finalized, however.
Read the full announcement on the World of Warcraft Forums.