Really the big disruption Bitcoin could cause if it becomes well established, is to act as a stable reference frame against which the other currencies can be compared
What would make it any more (or less) stable than the traditional reference currencies of gold, ammo, and canned baked beans?
The supply of bitcoins used as currency is fixed while the supply to all other reference currencies are variable in some way or another.
Fiat is obviously variable on the whims of the issuing government.
Gold may be taken out of circulation to make jewelry or electronics (or another use not yet discovered). Ammo and baked beans can be consumed. Bitcoin has no utility value and cannot be used for anything other than as a currency.
Similarly, the supply of these other items can be expanded. An asteroid full of gold could be mined, a new ammunition factory built, or a bean farm planted. Bitcoin has no physical identity, it cannot be reproduced, counterfeited, or grown outside of the well defined properties laid down in the original protocol.
Bitcoin is truly the first pure reference currency. Manipulative games can still be played with bitcoin markets, but the risk of external non-economic events affecting your money supply is removed. A political party can't decide the world needs more bitcoins, a new vein of bitcoins cannot be discovered, and nor can a new use for bulk bitcoins be invented.
Bitcoin prices will be no more stable than conventional currencies, because money supply is a rate (BTC / sec) rather than a total volume (BTC). As commerce using BTC slows down so the money supply decreases. As commerce speeds up so the money supply increases. The exact relationship between the money supply and inflation complicated and somewhat controversial (see Wikipedia for more info), but there is no doubt that if, for instance, all the people currently holding Bitcoins as an investment were to sell them then the value of Bitcoins would drop, because the money supply would increase.
What would make it any more (or less) stable than the traditional reference currencies of gold, ammo, and canned baked beans?