Well, it means that if nothing changes, then not only is the past an open book when a quantum computer becomes available...and as I said, there is nothing you can do to prevent that. It's gone. The past is gone. Forget about it. But if you take no action now, then in 10 years, whatever would have been sent so-called confidentially in the next 10 years will also become an open book. That's what I mean when I say that you cannot save the past but you can try to save the future.
Now, is it an apocalypse? It depends. For some things that are sent under the cover of confidentiality, if they are revealed in 10 years, nobody will care. If your credit card number becomes open in 10 years but you don't use it anymore, who cares? However, you might care to keep your medical history secret for the rest of your life. If you send anything that has to do with your medical history, and you care to have it secret for the rest of your life, forget it.
Of course, even more importantly, if national security data or whatever is sent without more protection, then yes, maybe it could be an apocalypse, depending on who the bad guys are who will use it whenever it becomes an open book.