Right. At this point, Bitcoin, as the first successful implementation of a decentralized cryptocurrency, has nonzero collectible, historical, and sentimental value. Personally if all 21 million were to be dumped on the market, I would bid against goldlyre to possess them all, and I'm sure so would several others. There is definitely a nonzero floor to the price.
Specific coins or private keys (e.g. Genesis block, even if unspendable) might have even higher value as collectibles. Who here wouldn't bid at least $1 in an auction for the keys to the first Bitcoins ever mined?