What will happen to Bitcoins, or more specific, to the price of a Bitcoin, once all 21 million are created?
At the exact moment the block reward drops to zero (around the year 2140), absolutely nothing will happen, since by that time the block subsidy will have already been an insignificant fraction of mining rewards for well over a hundred years. Instead, mining rewards will come from transaction fees. Part of the reason for the gradual reduction in the block subsidy is to avoid any craziness happening when it disappears completely.(1) At the moment we all talk about miners, GPUs, ASCIS, bulletin boards are filled with discussions. But once no new BTC are mined, will the price drop to 0? Because no one cares about BTC any more?
Why would no one care about Bitcoin when the block subsidy drops to zero (after it's already been insignificant for over a hundred years)? That doesn't make any sense.(2) BTC is meant to be a currency, right? But can I buy beer with it? Or a notebook? Book a flight? It seems all people do at the moment is trade it on MtGox, etc. - but they don't buy goods. No?
There are already many places where you can spend your bitcoins, and the number of places that accept bitcoins is likely to continue increasing in the future as Bitcoin becomes more widely known. 