This was discussed many times in the past. We are nowhere near quantum computers having enough power to solve private keys. This is maybe a decade away at least.
By then most of the etf companies which hold bitcoin in their reverses will upgrade to higher and more secure technology. But right now there is nothing to worry about.
So if I got you right, you’re saying ETF holders like BlackRock will just jump in and tweak Bitcoin’s blockchain code — all for our ‘safety’?
Remember how that went when SegWit came in? Plenty of miners weren’t on board, we got the Bitcoin Cash fork and a whole army of other forks. I counted 69 versions of Bitcoin back then. And BTC lost 50% in value. Good luck repeating that drama