Quantum computing isn't going to arrive for a few decades, and by then we'd have invented a tougher version of encryption that they can't break.
this is a commonly accepted but reckless assumption. it's based on extrapolating current computing trends and non-physical limitations. basically, you're completely writing off the possibility that technological breakthroughs in computing could ever happen. history shows this is an untenable position.
i'm beginning to prefer quantum computing FUD to these arrogant assumptions that quantum computing will never be a threat.