You know everything about the DS lite is pretty sweet. Never even remotely considered getting a DS until I heard about the new version. Still haven't purchased one, but when it hits $99.99 I'll likely grab one.
But regarding the original version. Considering the bulkyness of it, and the not as bright screens.... Will anybody really want the old one? I'm guessing if anybody wants to sell a old style DS, they are going to have to take a pretty big hit on it, cause any money spend on the old bulky version is money that could have gone towards the redesign.
Of course if you've had a DS lite for sometime, and are perfectly happy with it, then no worries I guess. Just keep on banging away on that bulky beast!