Nothing guarantees that a new currency will displace Bitcoin rather than complement it. A second or third or fourth crypto-currency with broad adoption like Bit

Nothing guarantees that a new currency will displace Bitcoin rather than complement it. A second or third or fourth crypto-currency with broad adoption like Bitcoin would help Bitcoin more than hurt it since they would suggest that crypto-currencies are here to stay forever. It's entirely conceivable that in the future there are half a dozen or more crypto-currencies out there that provide different qualities that make them more or less fit for use by different groups of people.