Zarhym made the announcement in a thread that explains the differences between 4.0.3a and Cataclysm.

World of Warcraft player Sammew posted a thread on the official World of Warcraft forums that explains what is and isn't being implemented in patch 4.03a. Zarhym responded to the thread and announced that the experience required to gain levels 71 through 80 is being reduced by 20% in the upcoming patch. He also mentioned that druids, paladins, priests, and shaman will have their talent trees reset.

Blizzard has made similar exp adjustments in previous expansions to keep the time it takes to level a character to the new cap from getting too lengthy. You can read Sammew's explanation of the differences between 4.0.3a and Cataclysm after the jump.

What is not in 4.0.3a:

    * Creating worgen/goblin characters
    * Worgen/Goblin start zones
    * Archeology
    * Professions past 450 (Illustrious Grand Master)
    * Guild leveling
    * Guild achievements
    * Eastern Kingdoms/Kalimdor flight
    * New Zones (80+)

What is in 4.0.3a:

    * Portals in Dalaran Removed
    * Class trainers in Dalaran where portals once were
    * New race-class combinations (excluding worgen/goblin)
    * New Gnome/Troll starting areas
    * Changes to existing zones
    * New cata load screens
    * New cata intro cinematic
    * New cata login screen
    * New music
    * City Quartermasters, with rep tabards
    * Bug fixes
    * Class balancing
    * Druids, paladins, priests, and shaman will have their talent trees reset
    * Experience required to gain levels 71 through 80 is being reduced by 20%
    * New tamable hunter pets (Monkey, fox, dog, and beetle, as well as new skins for exsisting pet classes. Complete list here thanks to www.wow-petopia.com: http://www.wow-petopia.com/cataclysm/newlooks.html)