I think prices need to go up significantly or else the total amount of bitcoin in circulation won't have a high enough value for them to be used in a significant amount of trade.

If there is only $43 million worth of bitcoin, then millions of people cannot possibly have enough to use in trade. If the value increases to $2 or $3 billion, then what we consider a low value amount of bitcoin now, e.g. 0.01 BTC, will be enough for a substantial trade, and there are enough bitcoins for a large number of people to have at least that much.