It never will, sad but true.
I have been doing this for years and I have "retired" so to speak from selling gold in wow, it is now by far the worst state it has ever been and will not recover.
If you want to get into this sort of business I personally recommend other mmorpg's, far better out there and there's more than one.
You could of made a mint from this game years ago, but there's no way now that's possible, too many botters and too little gold sinks, too easy to farm, everyone know's where to sell, where to farm, where to get the most profit ect. Way way too easy for newcomers. It's just suicidal.
I have 2 botting account's left from 20+ a few months ago, I just don't renew them anymore, I even sell gold on my main account's and not vanilla's as I just don't care, It's so not worth it spending money on the game for $$$ anymore with returns that can actually equal in a loss, these 2 account's will run to their death, when they're gone, I will never touch the game again.
Gotta say this game was fucking incredible once upon a time to make cash though, feel sorry for those people who never got a taste of it, you couldn't sell gold fast enough and the prices were fucking amazing.