What I'm looking forward to most are three things:
I'm looking forward to the hard push to level my main and my main alt so I can raid again. The fast grind of it with my guildies and friends and the support system and late nights on vent to get to 85, all the discoveries, and "One more!" dungeons, the screenshots on the forums on the dings, the cheering each other on, and just the whole process. And then the process of go go go with gearing so we can raid, leveling professions, and working together as a team.
I'm also looking forward to all the new zones, the old zones being like brand new, and finding little easter eggs, new pets, mounts, and other fun things like RP outfits an things like that.
Lastly I'm looking forward to my alts! I'm really looking forward to taking my priest who's just for PvP in the new PvP zones from 80-85. Some of the new battles look amazing! But most of all, I'm really excited for a worgen druid! I've always wanted a druid, but could never get into a night elf, and the worgen level areas look amazing! I'm also really excited to go through all the changed alliance quests from a lowbie perspective as I'm leveling.