Helms with sockets will increase in price; with a bias toward legendary helms such as HOC and Storm Crow.
Rubies, of course to go with that shiny new helmet.
Rings and amulets with added XP will also see a high demand. Good thing I bought 4 Obsidian Rings of the Zodiac...

The market is VERY volatile! Bought 20 mil in items. Sold about 10 mil. I think I'm just going to take a break and XP farm a bit. Holding assets till something interesting starts to trend or forecast...

I am so surprised about how gold price dropped in this week. It is below 1.4$/m I believe. I thinking how much fees I have paid in the gold auction house and how much gold I picked up since the beginning. Can I just assume that all the gold in the market is from bot/farmer?

@azwccc Yes. A large proportion of that Gold has to be gold farmers. The huge, quick drop is probably the gold farmers undercutting each other. They're all sitting on billions of Gold and as soon as they see the price dropping, they all rush to get their money out at the same time flooding the market and causing a market trough. It looks to have stabilized at around $1.20-$1.25 USD for now.

The value of gold will continue to drop unless they implement a different method to utilize gold or make crafting stronger. Personally, I think they should just buff crafting (especially the 6 prop and legendary ones), but a few interesting ideas have been proposed:

1) Pay gold to reroll on an item. This would have to be really cheap on rares, moderately expensive on legendaries, and CRAZY EXPENSIVE on set items, but people would love to try to get CC on some of those rings/amulets/helms.
2) Convert gold to Paragon experience. This one I'm not crazy about because of the potential for abuse, but it makes it quicker and somewhat more interesting since you could have made a ton of gold from a great item you found, but you're still PL 15. Buy exp for 50 M gold and suddenly you're PL 35. Or something like that.
3) Create a new form of currency outside the RMAH. This one is probably the least likely to happen, but it's kinda cool. Basically, what they could do is create a new form of currency (let's call it Whimsy dollars) in-game and you use gold to buy them. What do you do with Whimsy dollars? Well, they would be like anti-gold so they could do anything EXCEPT BUY ITEMS. They would do things like allow you to customize your character, color your character, change your name, whatever... If you really wanted to do the items though, they could be used to buy items that would be account bound. This means you couldn't sell them on AH or trade them with friends... but they would be really cool. Like a +25% bonus to EXP on an invisible halo. Or something like that.

The basic idea is that because there is currently no effective way to sink gold and you can FIND GOLD throughout the game, it just accumulates (switching hands until someone doesn't see anything they want to buy/can afford). Since more people have more gold, the price of items will rise and the value of gold will drop. USD has real world value, so gold will fluctuate based on this and yeah, it's going to be worth less and less. If monsters started dropping 10k piles of gold, then gold would probably only cost like 25 cents per million. If they made crafting A LOT stronger (let's say Griswold's Masterpiece could roll 1500 dps), then it would be worth it to craft, even if the odds were pretty low. You would see some Griswold's on the AH legitimately worth 100M and you would say, oh damn, I've gotta at least TRY to craft that. People would spend money on that and the amount of gold in circulation would decrease.