I am a strong believer in HODL. I expected bitcoin volatility decreases as time goes by, I totally didn't expect such big price change in the past several days.
Is bitcoin volatility here to stay and not decrease?
Yes, here to stay for a long while. Bitcoin volatility is a result of Bitcoin fundamental value drivers (varying supply and demand on an open market).
This is no stablecoin with pegged value, nor a stock tied to a company's future revenues.
How much volatility? Hard to predict. There is no reliable VIX to Bitcoin, but could change if ETFs are introduced (feel free to correct me if wrong here).
Long-term (10 to 20yr plus) is likely the volatility could be lower, due to block reward halving and stabilization of new supply vs existing supply.