A post on Battle.net reveals the WoW Token, an upcoming in-game item for World of Warcraft to allow the ability to exchange game time for game gold. Here's how this works:

Coming soon to an Azeroth near you: the WoW Token, a new in-game item that allows players to simply and securely exchange gold and game time between each other.

Players will be able to purchase a WoW Token through the in-game Shop for real money, and then sell it on the Auction House for gold at the current market price. When a player buys a WoW Token from the Auction House for gold, the Token becomes Soulbound, and the player can then redeem it for 30 days of game time.

When you put a WoW Token up for sale, you’ll be quoted the amount of gold you’ll receive once someone buys it—you’re guaranteed to get that amount no matter how the market moves.

The WoW Token was created to give players with lots of extra gold the option to use it to help cover their subscription cost, and give those who want to purchase gold a way to do so from fellow players through a secure, easy-to-use system. The Token will be making its debut in an upcoming patch—in the meantime, check out the FAQ below for details on how it works. {/quote