Also depends how long it takes to setup the quantum computer. Is it quick setting up a 1028bit key cracking multiple qbit computer? Running it a few million or billion times to confirm your probabilities and that there is no noise?
But yes, a perfect and quick to setup quantum computer can crack quite a few types of encryption quickly. IIRC there are though some types that take a similar time to unravel as on standard turing machines. So changing algorithm is possible (but currently not worth the overhead as there is no risk or need).