Since I'm a theoretician, I'm very comfortable with your question.
The short answer is that what I talked about at length, this “harvest now and decrypt later” strategy, is not a threat to ransomware, because to do ransomware, you need to do it today. It is not as if, in 10 years, when you will be able to decrypt messages sent today, that you can go back and ransom people who have moved on to something else already.
To ransom, you really need to be able—today on the spot—to decrypt and then get information that allows you to blackmail or what have you. This would require quantum computers being available already. If there is not one, then this is not a danger at the moment, but when it becomes available it will be a danger.