Well, that sucks. So I guess the only way to secure my xpub key for my Trezor is to only view my balance on an air-gapped computer, correct?
Not necessarily, but if you want to be absolutely sure that noone gets your xpub, then yes.
However, only the xpub is not enough to steal funds, it does 'only' destroy your privacy.
Hopefully, they don't come up with an affordable way run and maintain a quantum computer capable of breaking traditional algos anytime soon.
Quantum computers aren't some kind of 'magic machines'.
They are comparable to normal computers, just that they don't work with bits (0 and 1) but with qubits (which basically just is a computer with more than 2 states).
They can not magically crack cryptography.
First there needs to be a prototype which can be run in a stable state. Then it needs to be further developed, because high end server are way more powerfull than a small quantum computer prototype (which doesn't exist yet).
Further someone would need to invent an innovative algorithm (for a quantum computer) which is capable of solving mathematical problems noone had ever an approach yet.
You really don't need to
hope that they don't come up with an
affordable way to run such a machine.
And not to mention the need of a proper algorithm to crack keys.