As an HT3 owner, I would love to hear "the beast"/HT4 but won't be selling my HT3s anytime soon, no matter how good the new kings of the Salk line sound. As was stated before, cost is prohibitive, even the HT3s were way over my intended budget. If I hit the lottery or something I would no doubt be placing an order, but even then I wouldn't be selling my HT3s...
So, yeah I think we will be seeing a few HT3s hitting the used market, once the beast is unleashed on the world, but I don't think there will be an overwhelming amount of current owners making the switch. I think that we might be seeing several used $10G+ speakers from other manufacturers hitting the market though.