I'm gonna give you all my Guide for making as much money with the Expansion just around the corner. I normally wouldn't do this, but since I've got so much money right now I'll go ahead and share my ways.
Firstly, If you have 70s use all your remaining Badges to buy the Epic Gems from the Vendor in Shatt. These sell for about 150g each on my server and since Badges are getting replaced this is a good way to make some cash from it since people are still buying them for raiding or such.
Cloth, I can't give you a good idea on the lower level cloth, but I can say sell your Netherweave! The Linen-Runecloth might go up, although Runecloth will go down initially with Death Knights starting at 55. Netherweave however will be depreciated due to a lack of general need.
FLOWERS(Herbing) Save these up! If you even want to buy some while its cheap. Inscription will use Herbs and with so many people who will pick it up first thing, They will be selling like hotcakes for the first couple weeks, then while they will go down, they will still be quite expensive. These can be saved until the Patch as Inscriptioning will become available to everyone on patch day. This is gonna be the biggest money maker with WotLK release. Go farm them, Buy them, Save them. Just get as much as possible before the patch.
Equipment, I recommend selling equipment right now. Alot of people will start buying stuff for their Death Knights right now so Two-handers, Plate, and One-Handers with Str as the primary stat will be good sellers to these stupid pre-Xpac buyers. 60+ blues will also be getting a boost in price. Many people will want the best gear they can get before the xpac so they will be willing to buy blues which previously they would not. As well, while 60- blues will increase, the rate will be much lower than 60+
Sell all Gathering Materials, EXCEPT! Herbing, As the xpac will slowly filter these out it's a good idea to get rid of these materials which will become more useless and less used in the xpac.
The rest is up to you and how big of risk you want to take on your investments.