After you reached level 85, there is a feeling that the game is over, since the dungeons are few, there are only 5 dungeons, throne of tides, the stonecore, the vortex pinnacle, grim batol, halls of origination, and lost city of tol’vir.
And is really not fun to do 2-3 the same in a row.
The dailies are few, for Ramkahen there is only 1 daily quest, and there is no way to get rep with them except doing dungeons.
Pvp-ers are the saddest, there is no pvp gear yet, and atm. pvp with no pvp gear means unbalance.
The fight are taking 10 seconds or less, and usually the class / spec with the most cc is wining. Priests, locks with fear / rogues are the top now.
Is nice however to see Twin Pix battleground, having the same mechanics as warsong gulch, meaning Blizzard learned their lesson and didn’t made a sota like bg.
For pvp realms though there is tol barad, a pvp zone like wintergrasp, there are lots of daily quests, and its recommended to do them in a group, at least with one more player.
There are some nice rewards, on top being a spectral horse / wolf for alliance and horde.
These informations kinda cover the answer to the question “What to do after level to 85″.
Or you can take a break and come back when people are geared for heroics, there is pvp gear in the game, and so on.