I already mentioned that we are covering items to stockpile for the 500 crafting patch on the forums, but here's the link again in case you aren't a member yet. We also are discussing what NOT to speculate on.
Here's an email I received that deals with a question I think could help you.
"Hi. I was just wondering how certain you are about the prices skyrocketing of tier 6 materials.
Also, if you are so certain, should i be pouring money into buying these materials and just sit on them
until the prices rise?
Pouring is a poor choice. I would suggest 10-20% of your total gold, but
don't go crazy. I would also do this slowly over time, maybe 100-250 of
a few items each day with buy orders.
If you're thinking about spending all of your gold on lots of tier 6 crafting materials right now, then you're doing the opposite of my advice. Don't blame me when you're broke!