The thing is, no matter what the exchange rate of BTC to USD settles at, bitcoin will still have properties that make it more valuable than USD. For me, bubbleBoy has given the best account for the hoarding scenario, deflationary expectations.

For those that argue that, essentially, the free market will value BTC to account for this, your missing the fact that the price can never account for certain properties of bitcoin, because whatever the price settles at, it still has those properties. Even if 1BTC is worth 1 Billion USD, a merchant will price a product in USD and in the equivalent BTC, based on exchange rate, and the BTC will still have those properties that make you value it over the USD, namely, deflationary expectations.

The only solution I can see it to provide a different force the stops people hoarding it, and makes them want to spent it. There are 2 universal properties people value that bitcoin could give them, that at the same time would make them want to spend it. First is low transaction fees. This is something Bitcoin already has. The second is ease of use. This is something that bitocion does not (yet) have. Even if it did, USD already has this. A niche use case (for the general population) is anonymous payments. Bitcoin will always be the preferred payment there.

My prediction:
Bitcoin will always have 'hoarding forces' acting on it, but it will also have 'spending forces' acting on it. Thus, whenever there is a tie in the forces (which depends on the situation), and a product is available in USD and BTC, the user will choose to use USD. I don't think the hoarding forces for BTC will be as strong as they are for gold.