Who knows what the future might hold. I don't have the technical knowledge that OP and AverageGlabella clearly have but I can say this.
50+ years ago my father used to work on these big bastards, the source says that it could store up to 5 MB of data.
https://www.reddit.com/r/interestingasfuck/comments/6z95zz/first_computer_by_ibm/
He was a programmer and wrote programs for these computers. He had health issues so he had to retire early. He hasn't been interested in computers and never showed any interest in using one ever since which I frankly find unbelievable but it is what it is.
The first time I bought a USB stick and he saw it he asked me what it was.
So how much data can you put on that thing he said?
1GB! He just stopped and looked at me trying to figure out how much that is in B or KB because those are the two important units that mattered to him back when he was working.
What I am trying to say is although it is impossible to imagine quantum computers being a threat to bitcoin now, who knows what advancements will be made in 40-50 years. My father and his partners knew about KBs and a 5MB storage device taking up the whole room was probably the most advanced thing they could ever think about. They probably didn't even dream about a pocket sized device that you can plug in in a small opening at the side of your laptop (what in God's name is a laptop)!