With the advent of the Burning Crusade, flying and epic flying mounts at 70 became a sink for the extra gold floating around Outlands in player's pockets. There has been speculation ever since about what a similar sink might be in Wrath of the Lich King.
In jest, Nethaera put forth the following:
Animal rescue centers will be set up by D.E.H.T.A (Druids for the Ethical and Humane Treatment of Animals) and the movement to rid the world of Nessingwary will need funding! Save the penguins! Save the world!
Considering what a pain the Nessingwary quests can be, it's almost sad that he gets to continue recruiting for the butchering of beasts. Still, at least there will actually be penguins to "save!"
She also hinted at some of the actual possibilities for our next big purchases. Inscription will be the next trade skill, which will likely see many players dropping other professions and paying to level it, as well as all players shelling out hard-earned gold in order to purchase inscriptions on a regular basis.
Similarly, many players will start a Death Knight alt, and use their mains to finance its gearing, enchanting, inscribing, professions, and other expenses.
Neth also suggested that new mounts might be a factor, although we've already been told that Northrend mount attunement will be affordable. She also mentioned that the new hairstyles might find you parting with some of your gold.
Already, in preparation for WotLK, we are seeing more reasons to spend, spend, spend. With Haris Pilton finally live as of this afternoon, players will be flocking to purchase her 22-slot bags (1200g a pop) and other wares. Will you be saving up for Wrath, or decking out your characters with new bags?