For the sake of discussion below, I am ignoring the market forces due to Engineering and Blacksmithing, as goods produced from these professions have limited demand compared to the Jewelcrafting market (at least with respect to the common raw material of Elementium Ore). Simply put, one cannot liquidate crafted gear in great quantity as one can with gems.
Clearly, we will see a reduction in demand for ore if this change goes through, due to the lower price floor of prospected gems. However, we cannot assume that only the demand curve will shift. An unknown factor is how much the supply curve will shift. Farmers will still farm, but what price point will cause them to give up or enter other markets (i.e., Herbalism/Skinning)?
Furthermore, uncommon gems have rather limited use: jewelry, meta gems, transmutes to rares, and daily quests. Meta gems and daily quests have limited demand. Transmutes may see an uptick, but only for certain colors. This leaves jewelry. I forsee many Alicite Pendants being disenchanted in the future, since it is the only viable route to get rid of excess Alicite. As the price floor is 3g for the materials used to make Alicite Pendants (1.5g for setting, 75s per Alicite), and at a yield of ~1.5 dust and ~0.5 lesser essence per disenchant, Enchanting materials may also see a significant reduction.
(Alicite Pendant chosen as an easy example above. Carnelian Spikes may have a greater impact, but Carnelians are also tied to Inferno Ruby transmutes.)
We are still in the first week of the rather massive nerf to the basic shuffle and the safe floor price of Obsidium being cut in half and Elementium being knocked down by a fair percentage as well. On my server I have seen a very steady trend of decreased green gem prices (with huge variations, Carnelians are posted at 25g+, over twice the norm before the patch, and gems like Alicite, Jasper and Hessonite dropping well below 9g). We've also had two JC dailies in a row using Zephyrite and it is still going for around it's pre-patch JC daily price of 16g avg.
An interesting thing is that the price of Obsidium has been consistently high and very scarce. I haven't seen a stack under 45-50g in several days, while Elementium ore is still readily available at less than 35g a stack. Enchanting materials (excluding Maelstrom Crystals of course) have seen a very sharp spike in price, and have been insanely profitable. The nerf seemed to only hurt the people who did the shuffle and just sold all their gems to vendors. The people like me who shuffled all the way to DEing rings and necklaces and cut Rare gems are making out like bandits. And I am still seeing people post things like stacks of Alicite on the AH for less than their vendor value, and now they don't even have to cut it!
It is all very strange and I was terrified at first that this could totally ruin my money making, but so far it seems better. I think enchanting mats will calm down some, since there are a lot more people enchanting stuff now. But most of it depends on how people react by dropping professions (possible? I don't really know) and the farmers.
I am only in the Ore/Gem/Enchanting market, so I don't know if a lot of farmers are moving to herbs or what not, but this is definitely a good time for some. 200g Inferno Rubies is a thing of beauty.
Oh, and it may be a little late to really cash in on this for some servers, but you may still be able to make some good money by selling Chocolate Cookie for the achievement if you've been good about doing your cooking daily. They basically cost nothing but time to make and they are still close to 2g each on my server. On the second day after the patch I sold them all for over 200g a stack.
I hope some other people can give their observations on how the Ore/Gem/Enchanting market is doing on their server. It is definitely not what i expected.