Personally, I think that mass adoption is going to push the prices up and reach a new ATH. As the supply is limited, by increasing the demand for Bitcoin is going to have a significant positive effect in its price. We should try to integrate Bitcoin as a way of payment method in e-commerce businesses at first. This is very easy and it can show results directly to the market.
Mass adoptation will really help the market to improve specially the adoptation by the government to the cryptocurrency. Investors will help the market but it is just for temporary and they have the power to control the price.
I dont think mass adoption become very easy because its related to government regulation and many government ban or prohibit bitcoin in merchant. Its true bitcoin price drop significantly in 2018 but its because investor panic and many people take profits.