Bitcoin wouldn't replace the credit card because no merchant in their right mind would forgo payments in USD for BTC with BITC's price volatility. Are you guys serious? BTC behaves more like a commodity or store of value than a currency. Everyone hoards it.
True under current conditions. Speculators buy it because it is believed that it will be useful as a currency in the future. As more bitcoin is used as currency rather than commodity, then the price will stabilize, or be more predictable, IMHO.