There are three things that are possibly going to occur if bitcoin ETF will be approved by the Securities and Exchange COmmission. The first is that bitcoin may increase in value because of the good news, 2nd is that bitcoins value will decrease in value or 3rd there will be no effect. So today what we have is only a possibility but we will see what will really happen only after it was approved.
I think the first possibility will happen If the Bitcoin ETF is approved, I doubt the second and last possibility will happen because I have seen amazing facts about this

ETF approval will allow Bitcoin to get new investors and the history of the ETF's tremendous impact will make speculators more passionate