Sell my current IRA/Roth IRA funds a couple of days before ETF news day. No capital gains to report - money ready to go.
If the ETF is approved, buy COIN as soon as it's available (when would that be?). Double my money within weeks.
If the ETF isn't approved, wait and buy GBTC after the big over-correction. Sell once it doubles and await the next ETF news.
Profit?
If you lose out, you only have yourself to blame, better that than missing out if evyrthing happens just as you predicted it!
I personally don't think COIN will double the price of Bitcoin. I also don't think that COIN being rejected will cause the price to half.
Good luck though!