But that was already the case, wasn't it?

Store those packets long enough and even ordinary, non-quantum computers will become fast enough to factor the requisite large numbers within a reasonable period of time to unlock the comparatively primitive encryption which had been in use back when the packets were captured.

We're really just saying that quantum computers could theoretically decrypt those old stored packets sooner than the non-quantum computers will be able to do it.

But the non-quantum computers will definitely be able to do it someday. Those stored packets are not staying encrypted forever, regardless of whether or not quantum computing is eventually made to work effectively and efficiently and economically.