The volatility of bitcoin won't end anytime, I think we have to give more time for more people to appreciate bitcoin and use in daily business transactions. At the moment, I believe some form of regulations can help make things pretty much stable than we have at the moment otherwise we shall experience more issues with the volatility.
Volatile can't be main problem if bitcoin want to adopted as payment. If seller want, he can immediately sell his coin after get payment from buyer. Main problem is people who still not familiar with crypto.
Volatility is definitely an issue and a bottleneck for mass adoption. However, the bigger issue is the government regulation. In majority of the countries, crypto currency is not a legal tender or there is no legal framework available for cryptos in those countries. That is the reason why a lot of merchants are not comfortable to accept cryptos as a mehtod of payment. The same situation will not change until the respective governments come up with a regulation plan. If we want to see mass adoption, regulation is the first thing that needs to be taken care of.