How long do You think it will take the economy to settle down? Seems impossible to make gold via auction house. Do really all players now skin and then vendor skins for extra gold?
I think once there's enough people at 60, things settle down. Mats for leveling professions and leveling gear will go up in price because there won't be hordes of people leveling who are awash in these items. Why buy mats when you can just get them yourself while you're out leveling? Answer: you don't, and nor does anyone else.
Not sure selling low level crafting mats will actually be worth it later, as the only people who would be buying them and not acquiring it themselves are those who are learning new professions at high level, which will happen but it's not going to be a ton of people at any given time.
Also it helps once people are raiding, etc. Once people don't have the time to be out in the world 24/7 getting resources, they'll start buying them. The reason you could make lots of money selling low level crafting mats in later expansions like Wrath, Cata, and MoP, is that a lot of people are leveling in 5 man dungeons and aren't out mining Elwynn Forest or whatever. So they would need to buy the mats for their alts from the AH.
TL;DR - Not sure on specific time, each server is going to be unique. But once people get 60 it will be easier to make money.
It's gonna take a few months for prices to stabilize.
Now is the best time to buy low level crafting mats or rare BoE items if you have the money and are willing to sit on them for a while.