Unless you've taken a copy of every email, transmission or communication over many years abd then can decrypt that content at your leisure.
Now that the majority of encryption, by volume (i.e. HTTPS to the most prolific websites) is using PFS, you'd better have a lot of leisure time. Even with Shor's algorithm, breaking all those session keys would not be fast. Poly time is bad for cryptography, but it's naive to think that a large GQC will decrypt an enormous volume of stored traffic by magic.