I don't think bitcoin will ever be used as an actual currency because of it's built-in deflation. Deflation promotes speculation and hoarding of money (coin), which is absolutely the opposite of what you want in a functioning economy. I don't see any of the deflationary coins ever gaining traction as an actual currency, capable of supporting a market. On the other hand, the bitcoin protocol may prove to be useful in the future, and a more mature version of it very well may usurp the existing monetary system. I do believe we're a ways out from that at this point in time.<p>I think bitcoin, as a currency will fail eventually, but that the protocol itself and the encryption methods will evolve. The benefits of being distributed and efficient are too great to be ignored, but there's a lot of revision to be had.