Now, of course, everything we know is subject to change; however, just looking at the guild changes and some of the profession work that's been done, I am starting to have thoughts about what auctioneering is going to be like in Cataclysm. For one, having a guild bank will no longer just be for storage!
Guild perks for auctioneers
Here are the perks that Auctioneers will want to gain on their guilds, assuming it's not going to cost them more than it's worth.
Working Overtime Increases the chance to gain a skill increase on trade skills by 10%. This could be huge! I can certainly see myself temporarily putting a crafting alt into my storage bank to reduce the cost of leveling professions.
Bountiful Bags Increases the quantity of materials gained from Mining, Skinning, Herbalism and Disenchanting by 15%. This is almost as huge, because over any given expansion, while I power level several professions, I am constantly disenchanting. I imagine this will continue, judging by the peek I took at the data-mined enchanting recipes.
Bartering (Rank 2) Reduces the price of items from all vendors by 10%. This is nice, but won't be a huge game-changer for me. Still, I got my start by buying cloth, making bandages and vendoring them. Assuming this works when buying and selling to NPCs, it could be great. Even if it's buying only, I've spend over 10,000g on parchment since I became a scribe. And I started late in the game and, aside from my initial research, have been eschewing the glyph market.
Mobile Banking Summons your guild bank. 1-hour cooldown. This is no game-changer, but assuming I could get it with a minimum of effort, it would allow me to take advantage of lower lag areas to do my crafting. Aside from saving a few minutes of transfer time between the bank and the mailbox/AH, however, this won't do much for us and probably won't be worth it.
If the first few levels of guild perks are really annoying for a single person to get on their own, I suspect we might see more guilds and auctioneers pairing up. Actual functioning guilds have a lot to offer auctioneers; however, the auctioneer can't simply use the guild bank as a dumping ground for storage. Still, if I had to choose between two cheap tabs worth of space and the ability to proc more mats when I disenchant, I'd probably be better off with the mats.
Preparing for the profession changes
There's a whole post in how to prepare economically for Cataclysm, but I'll limit myself to what you can do to prepare your business and cover what you can do to profit off others' businesses later. Obviously, we're going to need higher-level professions alts: 75 for alchemy (and presumably all the other crafting skills), so get your alts where they need to be before Cataclysm launches and you have better things to do. Also, if you have any profession slots on a high-level character you're planning on dropping or one that you've never used, consider prioritizing gathering skills while waiting. The single time in the life cycle of an expansion where gathering is more money per hour than auctioneering is the first week or so of an expansion. People will be paying absurd amounts of money for herbs, ore and skins. If you're tempted to just use the stock yourself, don't. Unless you really need to race to a 525 crafting skill, you're better off selling the mats you get farming the first week, and then use that money to buy double the amount when the supply starts to increase.
So what are your business plans for Cataclysm?