Some things I imagine are obvious, but just want to toss out here anyhow:
1) Old World herbs/ore/skins will decrease in value now that we can fly in the Old World. While Worgen/Goblin profession leveling may have an impact, the days of Mithril and Thorium being insanely overpriced will be gone. Because they're even easier to farm than the new ores, their price will be capped by the new ores.
2) The way the Justice and Valor points are structured, there's nothing to buy with Justice points for raiders after you have your dungeon gear. With the 10% guild bonus, if rare gems are put on Justice vendors, this combined with the RDF could result in rare gem prices getting capped quickly.
So at a first glance, one could reasonably surmise that the most valuable volatiles will be life, water and earth, since barring mob-farming, they come only from herbalism (life) and mining elementium (life/water/earth). Shadow and Fire will likely be much more common around the board, as they come from your basic mining node (obsidian). They will probably be in somwhat high demand at first though, but I think life will really be worth mining early on.
It depends on what the demand-side looks like, as much as the supply side. Recipe counts are incomplete in Wowhead, and what really matters is which recipes people make. Life is used for Darkmoon (40 life) and Flasks (20 life), so I agree that that's key. Earth appears to have been removed from making Jewelcrafting pieces (unless that's how you make Jeweler's Settings). With that change and having the RDF from the get-go, I suspect demand for Earth might be lower. It takes 50 Fire to make the new 22-slot bag, so I imagine that'll bump up demand there. The Tailoring cooldowns have been spread out, so that there are 5 per week, and each one takes a different 30 Volatiles. This will spread demand more evenly. Also, Volatiles are not involved in crafting the new Meta gem.
More on the Tailoring CD - Dreamcloth is the new cooldown, and there are 5 Dreamcloth CDs on separate weekly timers. Each CD is in its own zone (though we don't know if there's a specific spot in each zone yet), and takes 8 Embersilk Bolts and 30 Volatiles. One (1) Dreamcloth per spellthread, two (2) each for some different 359 Rares, and five (5) for a 24 slot bag (shouldn't really be price-limited by the existing 3000g 24-slotter). There's a new 22-slot bag as well.
Alchemy - Cauldrons require one of each of the 4 Flasks to make, and Big Cauldrons require 3 of each Flask. They're not implemented yet, but if that's 10/25 for an hour, that's probably not going to bomb Alchemy, and it'll bring the Flask prices closer together. Guild Cauldrons are the big question mark though. If they're implemented at a static price, that'll have a major impact on Flask prices. Also, each Flask is made singly at a time and they're hour-long flasks. Each of Cinderbloom, Azshara's Veil, Twilight Jasmine, and Whiptail are used in batches of 8 in two Flasks (each Flask takes 20 Life, 8 of two herbs, and a Vial). Since the Flasks are +300 to a primary stat, that'll basically split the physical DPS Flask in two. However, there is no +Spirit or +MP5 Flask, so all Spell DPS and Healers will be using the +Int one, Flask of the Draconic Mind. We can expect that one to dominate sales, so that'll boost Azshara's Veil and Twilight Jasmine prices - those will be the herbs to shoot for.
Runecloth - I'm not in the beta and didn't find info on this, but if the new factions have the expected Runecloth turnin for reputation, runecloth might go for a hefty premium for folks wanting exalted with the new factions asap. It's worth noting that Worgen are a bit less likely to create a huge demand since there's no Worgen faction mounts.
According to Wowhead, these quests are not currently in the game.
Before you start getting crazy with the stock piling of mats, the guild achievement and reward is to make cataclysm flasks.
On this note, the only guild achievements it's been confirmed you can do pre-Cataclysm are the Reputation ones and the Legendary ones. So if your guildies all grind unique factions, you'll be able to get a leg-up on guild XP and guild leveling, which brings tasty treats like mounted move speed, more XP/rep gain for kills/quests, in the first few guild levels. The way I see it, there's going to be a strong incentive to reach Guild Level 14 ASAP, because that's a 10% increase in your skill-up chance. So when you're leveling professions, having that a few days earlier could be huge. Of course, that depends on what the Guild XP curve looks like - if it's going to take two months at the daily cap to hit level 14 anyhow, then doing it in 59 days instead of 60 is no big deal, but if it takes like 2 weeks at that cap, then this becomes reasonable.