I know we like speculating ourselves and the goal of speculation is to guess a winner but there's other benefits to trying to predict what items will increase and decrease in price with patch changes.
Take, for example, Black Lion Chests.
Over Halloween you guys will have noted that during the event they held a pretty low price point. Higher than now, but only by a few copper.
The real spike was just before the event landed - when people had heard and speculated that the chests were going to be oh so expensive. Imagination and speculation drove up demand and they soared to 30 copper each.
That was the first time we'd seen this kind of thing with new content and each time you can bet that the spike will be lower but we're already seeing movement in black lion chests now. The announcement doesn't even mention chests but that could be a double bluff (and so speculation goes on :P)!
There will be other opportunities, chests are the first but I'm noticing movement with piles of putrid essences too. I love those essences! I've a stock of 1,000 myself from close to vendor price but there's no way of telling if these are going to be needed in this patch or a near patch.
It's speculation (some believe it's pump and dump too) and lots of players are doing it every day. Speculation is powerful.
This is the first way you can take advantage of speculation. You figure out what people will logically assume will be needed for a new patch or for new content well in advance. Stock up on those items when they're still at their 'Post Halloween Low' kind of levels (think chests before the last Lost Shores announcement) and then sell when the speculation is reaching a peak - not when the content is launched.
It's a surer bet than waiting for the content to hit and watching prices plummet.
You can benefit in another way from speculation.
Look at the guesswork going on elsewhere. Orichalcum is falling in price. There are numerous theories about this. Some say it's only natural - more players have multiple 80's and can farm more. More servers have Ori maps that make finding it easier.
At the same time, players have been told about this new tier of materials coming with the Lost Shores content. A lot are worried this'll reduce Ori's value: "Dump Ori now" is something I'm reading in a lot of places.
I'm not fully behind this. The fact that there's some new nodes doesn't mean Ori won't be needed. Look at the types of items that Orichalcum makes in the mystic forge. Some of them look incredible and still will even if new resources become available.
I'm not advocating you buy Orichalcum (yet - at least not at the current price) but keep your eyes on it. You could stock up on a valuable material while negative speculation is driving the price down then wait for the market to stabilise when there's little actual change in the supply/demand for the material, bringing the price back up.
Lost Shores is content where speculation is more tricky and price movements are going to be all over the place - there's no theme to the items that will be popular after launch. We'll have to check as many resources as we can for word on what the masses are going to speculate on.
But the Christmas event - that's themed and much more predictable! Eggs, cinnamon (and other traditional xmas spices), snow truffles, butter (all that baking), anything mentioning snow or that's involved with Christmas festivities at all, are bound to spike before the content drops and now's the time to get them before the first wave of speculators start moving.