BitCoin should not aspire to replace money (what is money: gold, fiat?), but aspire to replace what works as money (= the money supply, which includes credit).
Money is whatever people agree to use as a medium of exchange. Thus, bitcoins are money.
The problem is that credit constitutes the vast majority of the (fiat) money supply, not cache. BitCoin should not be overwhelmed by the same issue (because that credit is a centralized monetary mechanism).