July 11, 2018
A Bitcoin-backed ETF on regulated exchanges is a worrisome prospect due to ongoing "anomalies" in Bitcoin's price, which appear to be the result of price manipulation using methods which would be illegal on regulated exchanges, e.g. wash trading.
I would draw your attention to this study, which uses statistical methods to attempt to answer questions about whether Bitcoin's price was (and still is) being manipulated at the time of the price bubble at the end of 2017:
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3195066
While I would love to see a path towards creating ETFs out of digital assets in the future, I'm not sure it makes sense to create one out of something whose price is actively being manipulated.