Some group of people has argued we will experience another high surge in Bitcoin Price early 2019 when ETF get approved while some said ETF does not have any crucial role in influencing Bitcoin Price positively.
Bitcoin ETF approval would greatly increase adoption and would draw in investors of different scale.
But I doubt it would have any significant effect on the price, especially in the long-term scheme. Sustained price stability and consolidation of bitcoins value is one of the goals of the asset, and ETF wouldn't accelerate that.