Bitcoin is volatile and the current bitcoins value is just temporarily stable. BTC at the moment found itself at the support zone and at a time surprise it holders of it potentials to soar higher in the future. BTC is not relatively stable and cannot become a stablecoin.
Probably, people need to understand the meaning of something before they even ask a question which in this case, I am not sure the OP tried to understand the meaning of stable coin before asking that question. Bitcoin is bitcoin, and even though we end up experiencing some level of decrease in volatility over time, which I believe is not even anytime soon, that does not make it a stable coin.
A stable coin is a coin that is pegged to a physical entity, fiat or asset as the case may be and that is what makes it a stable coin. So, considering that because we are seeing some small fluctuation as stability is even absurd.