Of all of the crafts(wo)men, Scribes may feel the effects of the patch the hardest. If you currently make your money by selling glyphs, then I would work on selling your entire stash off pre-patch.
Once dual-specs become a reality, people will no longer need to purchase new glyphs every time that they respec or spec back to their mains. They will simply glyph each spec once, and never need to purchase glyphs again unless they switch to their least-used spec, or a new one becomes available. At first, it seemed that you would be providing portable Lexicons of Power as a requirement for dual-speccing outside of a city, but that requirement has been removed.
Once you've sold off your stash, it is time to start building up a stash of inks. Patch 3.1 is introducing a whopping number of new glyphs as well as changes to existing glyphs. You'll want to be ready on day one to start cranking out the most popular glyphs, as well as the new ones, for a handsome profit. Everyone will be re-glyphing their main characters and pimping out their new offspec, and demand will temporarily spike.
When this subsides, hopefully Blizzard will introduce a new way to make some income!
Because of the widespread boredom over current raid content, the prices of herbs have been falling on the Auction House. If you aren't an Herbalist, or don't feel like gathering, then now is the time to buy in order to buff up your ink stocks.
You also might want to consider making your finest vellums. Either funnel them to a high-level Enchanting alt, or sell them. After all, post-patch, everyone will be clamoring for the new enchants, as well as constantly replacing their gear.
If you are an Enchanter, then I'd start looking for a cheap source of vellum! I would also recommend purchasing cheap Auction House greens now, rather than later, in order to build up a reserve of Enchanting materials.
Once the patch hits, Enchanters who sell materials rather than enchants will see increased profits. Everyone will be buying the materials for the enchants that they need, or the actual enchants on vellum. Enchanters will be buying up greens and mats to take advantage of the upswing in business.
If you want to be prepared, then start buying now, while the prices of greens and raw Enchanting mats aren't inflated. Start putting the most popular enchants onto vellum now, but save some materials for the new enchants that will come with the patch.
Your post-patch riches will not be restricted to patch day, as people will be plodding through Ulduar upgrading their gear for quite awhile. Having a stash of materials saved up beforehand will lower your overhead.
As mentioned above, herb prices have been falling lately, and now is the time to buy them. If you have a stash to sell, hold off on the days where prices are particularly low. Once Ulduar becomes playable on live realms, the demand for herbs will soar as people will be snatching up new glyphs, elixirs and flasks.
Frost Lotus in particular should see a huge spike in price. Ever since Blizzard nerfed the drop rate, my usual stack of 60-80 surplus Frost Lotus has dwindled to around 5-15. Purchase them now, and sell them later!
Herbalists may as well herb pre-patch. Once the patch hits, those who did not prepare ahead of time will begin a strict regimen of gathering in order to keep up with their own, and their guild's, alchemical needs. If you save up now, the increased competition won't hurt so much.
Alchemists, of course, might as well start making up flasks and elixirs while herbs are still cheap. Flasks will be important to raiders who do not like to fuss around after each and every wipe, while elixirs will be marketable to those who don't care about the increased cost as much as they care about stat customization.
Keep in mind that mana regeneration is also being nerfed into the ground. While you might be able to sell mana potions now, there will likely be an increased demand post-patch.
Now is also the time to maximize your First Aid and Cooking, and even Fishing, if you haven't yet. While cloth prices have lowered, new Tailoring recipes are being added.
Many people have stopped bothering with expensive food buffs, but Ulduar will require their use. Whether you ever see yourself making strong profits from food sales or not, you might be able to buy some stacks of food and/or meat and fish cheaply now. It also wouldn't hurt to make up several stacks, as each wipe on the Ulduar learning curve will consume more food.
The patch will mean that people are upgrading their new gear again, and this will increase demand for gems, belt buckles, spellthreads and leatherworking kits. Item customization is big business.
Whip up a few scopes, Eternal Belt Buckles, spellthreads and LW kits, in addition to some of the most popular gem cuts, depending on your profession. If there are any recipes for these items that you do not yet have, now is the time to grind the reputation for them.
Uncut gems and likely, raw ore, will sell for more post-patch. If you can, increase your Mining time, and start Prospecting! Red gems in particular should be saved.
Each week, Insider Trader takes you behind the scenes of the bustling sub-culture of professional craftsmen, examining the profitable, the tragically lacking, and the methods behind the madness. Check out the patch 3.1 profession changes.