Auction like crazy before Cata comes out?

Ignoring the cash implications, I'd say you want lots of space in your guild bank for people to dump the new items. Keeping it full of old junk on the off-chance you can sell things will not help anyone.

Professions are not yet updated so it is anyone's guess what raw materials people will need. About the only thing that is sure is that high tier items only used to craft current end-game items will become almost worthless. Flogging all your raw materials will net you more space for Cataclysm and remove the risk that it will all become useless.

Current blue and green item BoE items are unlikely to be used by guild members so I'd say clear them.

Quest are all changing so old tradable quest items are probably selling at a peak price now, as achievement hunters try to clear Vanilla content.

When my guild normally enters an expansion we normally clear as many tabs as possible to allow our members to donate things. The only thing we don't bother removing are consumables. We let our members grab those to use as they want while leveling.

The one thing I've found so far in the beta, considering the prof's have not been updated as of yet, is the lack of world drops. Meaning the mats you get leveling, or from quests, such as greens to disenchant or various other base mats used by the profession, aren't dropping from killing. Granted, this is the beta so alot of things that will come up/drop in the live version simply have not been implemented as of yet.

With that said, and considering this "expansion" -- as you said -- is more of a revamp of old content, I would think that holding on to older stuff -- for your Goblin's and Worgen's -- is wise to an extent. I'm not saying to stock your GB with nothing but old mats/gear and etc, but keep some of it. Everyone's gonna wanna to at least try a Goblin or a Worgen, and with that will come the professions, so having some of those mats handy will only benefit your guildies.

Personally, as I have several "guild banks" that I own personally on the live servers, I'm having my guildies mail that stuff to me for storage for the time being. I'm leveling a Goblin and a Worgen and making note of the things I need -- as I've leveled all but Engineering to 450 on live -- and having them stock pile the basics. My guildies are happy to do it, and in the end if the prof's update to the point that we won't need those things once Cata is live, then there's always the option to sell. Granted we won't get as much, but still...every copper helps.

The best short term strategy, based on my experience, will be to unload everything you won't be using to level a new character. That will give you lots of room to store the new mats & drops to stock pile & trickle into the new market. Keeping the mats needed for leveling the profession you want on a new character though is cheaper than selling now & buying later in most cases.

Long term, at least on my server after BOTH expansions had been that prices of lower level mats start to increase not to long after people hit the level cap. Around the same time Prices on new mats begin to drop. Many old world / BC mats on my sever ended up being more expensive about 6 months after the expansion than they were leading up to it.

All of that should make since since as people top out they will start grinding for mats, lowering the cost of higher level stuff. With the gold they make many people will just buy the mats for their lower level characters so they don't have to grind more.... Something to think about when playing the market and trying to wait out prices.

It depends on what you're selling.

1. Wrath progression items (Primordial Saronite, BoE epics, etc.) While prices for these are at an all-time low in most cases, they're never going to go back up again, and after Cataclysm hits they'll be more-or-less worthless. Sell them now.

2. Raw materials for Wrath/TBC professions (Saronite Bars, Lichbloom etc.) Even when Cataclysm hits, people are still going to need them to level their professions (while it's true that professions are being revamped, it's unlikely that they'll completely change the raw materials, and most of the changes are going to be focussed on the old-world). At the moment, prices for these items are relatively low, as most people have already maxed their professions. However, in the first lull in Cataclysm people will start levelling again, and you'll be able to offload these at a much higher price as fewer people will be farming them. You may think that these are worthless items, but a month or so after people hit the cap they'll be worth more than they ever were. Keep as many as you can for now.

3. Consumables These can be used to help you level from 80-85, so I recommend you keep them until Cataclysm and then use them as fast as possible. Anything left when you hit 85 can be sold for whatever meagre sum you can get, or just mailed to alts passing through their useful level range. Keep for now (unless you really have no space at all, in which case sell them).

4. Old-world mats. These are the hardest items to decide upon. They're the ones most likely to be affected by any profession changes, and they're the ones which will, most likely, sell for the least. I'd wait for more information for now.

5. Cataclysm mats (that you collect while levelling.) Mats will be at their highest price during the initial levelling period. If you can't use them yourself, and no one in your guild has an immediate use for them, sell them straight away. You may be tempted to keep them for later, but it's actually more economical to sell them at the high price, and use that gold to buy more mats later when the price drops as everyone finishes levelling.

Hope that helped,

~Roxton.