The price will only get stable as more people join in, and more money gets into the market. That's why I think ETFs and every other means that could bring institutional investors are a good thing for bitcoin, even though they probably don't care about bitcoin potencial, and are coming in just for the trading opportunities. If we get a lot of liquidity, it will be much harder for one person or a group of individuals to change the market, so BTC will get more stable.
This sounds logical, except that as more people have joined in and higher inflows are recorded, Bitcoin price has entered a new period of consistent volatility. Just a look at the charts show that the swings, which used to be far apart, are now taking place in shorter periods, from weeks, to days. Derivatives aren't going to contribute to Bitcoin liquidity for actual holders though - not until they move on from cash-only settlement.
For me, we have to move on to decentralised markets with transparent movements of funds if we want to eliminate (or at least make it more difficult) for manipulation. At the moment, data is at best incomplete, and it's hard to tell what's really going on on the back-ends of the major exchanges where the majority of volume lies.