[mcdigman]

A better guess would be that the last new bitcoin will never be mined, because exponential growth in hardware dedicated to it will not last, given that the cost/benefit ratio (in terms of power, hardware, and effort) gets worse the fewer bitcoins you can mine per minute. And when people stop being able to mine them, their value will drop because people aren't making them anymore, which leads to it being even less worthwhile to mine them, until they are being mined too slowly even to hit the adjustment point - in other words, when the bubble pops, the currency will collapse completely.

So from that point of view, the last new bitcoin is likely to be mined earlier than expected - but it won't be the 21 millionth.

[mcherm]

If there were no transaction fees built into the bitcoin protocol, then that might be true. But the system is designed to slowly and smoothly transition away from funding the mining activities by issuing bitcoins to funding the mining activities by paying transaction fees.