Eh, not really.
A quick scan of the Internet—yes, all of it—shows no real deal trends. Gearfuse was able to find one current gen iPhone going for less than $200, and one for $200; the rest are all over the place.
The second-hand iPhone market should pick up once July 11 rolls around, and not a day sooner.
Though Twitter is rife with “who wants to buy my old iPhone” tweeets. Of course it is.