I'll sell all my dvds on eBay when I decide to upgrade. For now this Columbia House sounds pretty appealing, considering I've been wanting to build my collection and just got their offer in the mail yesterday.
I also think dvds have more staying power than tapes did, basically because they were more of a revolutionary change over tapes than blue discs or HD-dvd will be to dvds. They will only make media look "prettier" with more memory capabilities. When media switches to a non-disc format is when an upgrade will be on my horizon.