If you have enough gold, you can control any market.
But, not sure how much gold is enough; I'd guess it to be a rather large amount.

Aside from a relatively minor cost for the thread, the formula holds true:
1x Stack of Netherweave = 1x Netherweave Bag.
To control the Netherweave Bag market, you need to control both Netherweave Bags and Netherweave Cloth.

To control a market, you'd have to choose a sale price.
And even if it cost you, purchase anything below that price point.
And re-list at the price you have chosen.

If you have the majority of Netherweave Cloth/Bags, then most auctions listed will be at your price.
Undercuts should be relatively close to the price point you set.
But you'll still need to buy them out.

You might want a whole bunch of bags up, just before the servers go down.
To feed demand, until you get back online.
Once you're online, posting and reposting smaller batches is probably a better approach.



The demand for bags will be largest in the first week of Cataclysm.
Beyond that, it will fall sharply.
But people will continue to create new toons, so you should be able to sell most/all of the bags, eventually.



Typically, new characters reach the 58 to 68 (Outland) level bracket at 4 to 6 weeks after character creation.
Which means, a large demand for Netherweave Cloth just prior to this point.
And lots of Netherweave on the market, after this point.

However, Outland and Northrend will be relatively dead again, after the leveling bubble.

I would therefore anticipate:
a) gradual increase in demand of Netherweave.
b) a price spike near the 4-5 week point.
c) the price tanking around the 5-6 week point.
d) the price settling close to where it is now, a few months from now.

Even if you have a large surplus of Netherweave after week 1, you will likely be able to move a lot of it in Week 4 and 5.