These are the announced changes we're planning in 2.3 for the Priest class.

Pain Suppression changes to be targetable on others, give 40% damage reduction and 5% threat reduction
Meditation to increase to 10/20/30% mana regen-
http://forums.worldofwarcraft.com/thread.html?topicId=1778036739&sid=1&pageNo=5#88

Power Word: Shield to gain additional benefit from spell damage and healing bonuses-
http://forums.worldofwarcraft.com/thread.html?topicId=1778036739&sid=1&pageNo=8#156

Prayer of Healing, Circle of Healing and Holy Nova (healing effect) will gain additional benefit from damage and healing bonuses-
http://forums.worldofwarcraft.com/thread.html?topicId=1777967050&pageNo=1&sid=1#8

Priest Racials- Change to Fear Ward and the Addition of Chastise for Dwarf and Draenei priests-
http://forums.worldofwarcraft.com/thread.html?topicId=1778047484&pageNo=1&sid=1#1

Priest Racials- Change to Elune's Grace to reduce the chance to be hit by melee and ranged attacks by 20% for 15 seconds-
http://forums.worldofwarcraft.com/thread.html?topicId=2040216056&pageNo=1&sid=1#6

Reduction in Mana Cost for Power Word: Fortitude, Divine Spirit, Prayer of Fortitude, and Prayer of Spirit-
http://forums.worldofwarcraft.com/thread.html?topicId=2040216056&pageNo=1&sid=1#6