If USD was limited to currency in circulation then it would not be nearly as inflationary as it is.
Once an established lending system based on bitcoins is established it will have the same problems as our current currencies. It wasn't printing money that caused the real estate bubble, it was the way to banking system has the power to expand credit and the systemic risk that expansion of credit causes.
Once there are fractional reserve bitcoin banks it will no longer be a deflationary currency.