Just read this from a news article - "Water levels in the three rivers should return to normal within 10 to 15 days, but it will take an additional three to four weeks for water to drain entirely from inundated areas, he said."
I wouldn't expect prices to start dropping for at least a month after the water is gone.
will hdd prices go down by december? you might "save" a few bucks on black friday or other sales, but hdd prices will certainly not drop back down to pre-flooding prices for some time, possibly not even until Q2 next year.
I would say HDD's are going to demand a premium for 3 months, that is how long the supply chain is for overseas imports. You may get lucky and catch a few less desirable drives on sale, this would be a great opportunity for distributors and dealers to offload some outdated low demand models that have been sitting in inventory for a while.