Small dump? Large dump?
It depends. Every evil, zionist banker shill in govt from Ben Bernanke to David Cameron has approved of bitcoin and wants the goyim to utilize it so every transaction you make can be tracked, and they know they can easily co-opt it to sidetrack you into their digital only, cashless society as well. If they believe an ETF helps them accomplish this task in some manner, or it allows them to more easily manipulate the price up or down, then an ETF approval is not so far fetched.
There's just been way too many government tyrants and zionist financiers who have given bitcoin the thumbs up for me to believe they have any interest in trying to stop it. Some of them want you to use it solely so you'll stay out of the already stretched thin gold and silver market. Other banker shills want you to use it because they think it accommodates people to a cashless only society or that they can co-opt it. I'd say it's 50/50 at this point.