If Bitcoin was to become a globally accepted cryptocurrency I think nothing else matters, the price of Bitcoin isn't the reasons why we should be using Bitcoin instead we should be using it because of its decentralized nature. We can always have other investment opportunities we can capitalized on beside trading the up and down of Bitcoin price.
What you say is Satoshi's original purpose in creating bitcoin, but things are going in a different way. Bitcoin has become a form of investment, and everyone is entering this market just for profit, including you and me. Most of us are here for profit, not for the decentralization it brings. If bitcoin becomes stable one day, I believe many people will leave it and find something that can be profitable for them. But either way, OP's hypothesis will never happen, so expecting bitcoin to become stable will never happen.