4.2 in a week?

Seems like patch should hit next week.
 If you haven't started prepping, now is the time.

Take a look at the MMO list that was created for the new 4.2 craftables to get a good idea of what to start buying on the cheap

No real surprises, Volatile Fire and Water seems to be the main with earth and life close behind.

LW needs tons of Pristine hide. See my previous post on how to buy up cheaper scraps and leather to get those pristines at much lower costs.

BS need tons of Elementium bars and hardened, you will be in competition with the JCs that will probably try to buy them up for prospecting and hoping for future epic gems.

Alchemists start doing your Truegold CDs (if you for some reason stopped)

Inscriptionists get ready to do another Northrend Research to get the latest Shaman glyph (Glyph of Unleashed Lightning) seems to be a really nice one that I will be using on my elemental Shammy.

Tailors either start stockpiling Dreamcloth again for the new items.

Enchanters looks like you should start crafting a ton of glove and feet enchants. Since thats what the majority of the new craftables fall under.

Good luck, and get ready while you can!!