The issue of stability of btc to me as I see it as mixed blessing in the sense that it has its own advantage as well as disadvantage. The advantage has attracted alot of people and it has make the investment in btc a worthwhile venture but on the other hand the instability could also not be distanced from the reason why a lot of merchants are not coming into bitcoin because they have to start adjusting their price every time to reflect the current position of the price which could change more times in a day...
Volatility and stability have their own advantages, that's correct, but in both cases people will be attracted to bring their money into Bitcoin.
Volatility attracts people that are looking for a solid investment option with high potential rewards, but if the prices becomes stable at some point, these people may leave.
But the stability on its turn will attract money from people looking for a solid store of value option, people that are more willing to use Bitcoin as currency, and the list goes on. In both cases money will flow into Bitcoin.
But just to come back at the merchant thingy, merchants don't have to care about the stability or volatility as they use payment processors such as BitPay to convert everything to fiat. It's risk free for them.