Official Patch notes can be found here

Oooooh patches! Have your computers open ready to download so when you come home you don't need to wait :) Click the link above to go see all the changes to your classes. 

The biggest thing to come is Timewalking: The Black Temple. You'll be scaled back to level 70 (and ilvl 141!) and get to enjoy the adventures through the old raid. 

There are new events: a fashion contest, celebrating all things moonkin, dancing at the auction house and my personal fav the in game version of the gnome run that I do every year :) There is a new pet battle dungeon too AND a new band at the Darkmoon Faire that you can compete against for goodies.