I have been for a little while been collecting some herbs, I have a herbalist but I don’t even actively do the herbing daily. I don’t have big stacks but I have a bit of everything. I do however make sure that everytime I’m in the area of a Herbalist Supplier in a city I check their stock.
Why?
Because often underneath the Vials are a small supply of basic herbs which I always buy, which Banana Shoulders Inscription guide indicates will be very usefull. ( Even the herbalism supplier on the Isle, if your lucky enough to get has some of the high end herbs in single or double quantaties rather cheaply.)
So I have a small stockpile of herbs but like those people who accumulated honor and badges in hope that they would be worth something for WOTLK, I could be wrong, what happens if Blizzard has something sneaky up their sleeve, and that those who are stockpiling the herbs for either personal use or profit are wasting their time.
We are about to have another main profession use a Gathering profession, and we know thats a demand increase right there, Blizzard seems all about trying to keep the playing fields as fair as possible, I can’t see them wanting people to profit from extreme demand that leveling inscription is going to place on peoples pockets and the worlds resources.
Imagine staking out spawning points in Elwynn, forest, Goldshire Inn will be doing a roaring trade as people stop in for the Goldrush. They will be setting up miners *cough herbalists camps behind the blacksmith.
I like the idea of being prepared, and I might be wrong, but I can see blizzard doing something extrodinary when it comes to the demand that inscription will place on herbalism, even if its just increasing the spawn rate. Nothing reduces prices like oversupply and competition
But.. I can’t remember if they did anything for Jewelcrafting, and the demand it put on mining.
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Pugnacious Priest's Warcraft Blog 
They didn’t do anything about the need for mining supplies when they introduced Jewelcrafting, no. I think everyone would welcome a boost to the ease of herbing. 🙂
That said, Blizzard have never interfered with supply and demand issues that make some people very rich, so I’d be surprised if they started now.
I have been doing the rounds on my herby for the past week or so, and haven’t seen that much competition for nodes so far (Darkshore has way more herb nodes IMO than Elwynn).
I cant remember what jewelcrafting did to mining either, because that was when I took a break from WoW. When I came back, things seemed to be pretty much the same, though …
Mining initially was used mainly for Blacksmithing; it was also used for Engineering, but that profession uses basically everything.
When Jewelcrafting was introduced, those cheap ores suddenly became heavily demanded, and prices skyrocketed. Copper bars went for 20-40 gold per stack, and the like.
After a while most new Jewelcrafters moved past the old-world metals and people who wanted to make money brought in tons of ore, and so the prices stabilized again.
The same will happen now; right before the expansion, prices of herbs will skyrocket as people supply and stockpile for power-leveling Inscription. A few months after Wrath, when all those death knight herb-nerders have levelled up their Herbalism and dumped their proceeds on the AH, prices will most likely stabilize at price levels slightly higher than now.
Of course, herbs not used in flasks were pretty cheap, but now that there is a profession that has a use for them, the lower-end herbs will increase in price more than the TBC herbs (which were already highly demanded for flasks).
My new druid just dinged 60, and I spent some “holiday time” by leveling her Herbalism to 300+, which gave me enough herbs to power-level two characters to 300+ Inscription (according to the guides).
I am ready for it!
^_^
Actually they did something against the general demand for herbs (even if it will hardly affect the leveling rush):
Potion Sickness!
If you can drink less potions, you need to brew less and therefore the total demand will go slightly back.
@dionadar
Well, that only would lower the profits and need for Potion masters. Elixir masters still will be in full swing. But yes, demands for potions will drop, especially with all hints pointing at a health and mana potion that has a cooldown instead of being used up.
If such a thing would make it on live, I can see Potion Mastery becoming a very quickly retired section of the alchemy market.