World of Warcraft production boss J Allen Brack apparently confirmed at BlizzCon session this weekend that paid character customisation is on the way to World of Warcraft. From this Warcry report:
When asked to expand upon a button found by sifting through the Lich King beta's data files named "Paid Character Customization," Brack initially hesitated to give any answer at all. Several questions later, he went back to the matter, saying that he could, in fact, confirm that World of Warcraft would eventually have some form of paid character customization, though they themselves hadn't yet worked out any details.
There's a full report of the panel through there.