I don't think this applies to the Fireworks/Sparks. There weren't many ways you could get your hands on them unless you lived in China/Shanghai. Most guys had to get them either through an overseas connect, Kicks-Crew, or worse eBay, and the prices for them haven't really come down at all. They started at about $300-325 ($200 something if you were lucky enough to have a connect), then jumped to $500-600+ after people started realizing they weren't gonna release in the US. Given how hard it is to get them for those in the US, I don't see the price on those ever really coming down cuz those are legitimately hard to get and especially rare in the US. They'll probably end up more along the lines of some other overseas exclusives, like the Barcelonas, that just continue having really high prices, even though I don't think they'll ever quite hit Barcelona prices cuz those were even rarer.
Prices on the WTKs will definitely start rising again once all the resellers looking for a quick buck sell off their pairs, and not as many WTKs are left on the market though. I'd let all the people who ordered off of NDC/FTL/etc get their pairs in hand first before jumping in.