The major problem is that the approval of ETF on 16th Aug is subject to speculation. Many experts are mentioning that it might get postponed if not disapproved. I think there would be a mix sentiment if the ETF gets postponed. There won't be a steep decline in prices, rather a small correction and BTC will start moving up again until the next date. In 2014 also we saw ETF speculations which was done primarily as a pump/dump scheme.