I think that depends on the extent to which quantum computer specific algorithms are developed for general purposes, and what specific technology ends up working for a large enough (enough qubits) quantum computer to be practical.
One school of thought is that QCs are only good for certain classes of computation, so would act more like a purpose specific component in a standard computer. Similar to the way a GPU is utilized specifically for graphics rendering (and those other parallel applications like machine learning). Most regular applications and most of the operating systems barely use the GPU, relying mostly on the CPU. A “QPU” ( I have not heard it called that, but it's a probable name) could be called into action when the computation required is appropriate.
My understanding is that currently these machines are enormous, have very large energy requirements and very low processing power (only a few qubits). A lot of them employ exotic materials or require super cooling. I tend to think there will be some breakthroughs in that area, if it hasn't already happened.
One of the most discussed applications is in cryptography. Many forms of encryption rely on the difficulty in finding prime number factors of very large numbers. i.e. take two very large prime numbers and multiple them to get an enormous number and use that number to do the encryption, but require the original two prime numbers to do the decryption. QCs could apparently do that task — factoring — very quickly, rendering current encryption methods worthless. It doesn't take a big leap of the imagination to suspect that military and governments and other organisations would be very interested in both having that capability, and preventing it from being publically available. To know everyone else's secrets yet still keep your own. That is fairly inevitable, but it the meantime whoever has that ability has the upper hand in intercepting communications. After that transition period, we will require quantum communication methods to replace traditional encryption of communications and that advantage will disappear. Those quantum communication methods are fairly well advanced in research, and are literally spooky action at a distance. One experiment involved entangling lots of pairs of photons, beaming half of them to a satellite in orbit, and then manipulating the earth — based photons and measuring the same changes in the satellite photons. The accuracy is fairly low, something like 60% but there are error correction techniques that can be applied. The communication between entangled particles is instantaneous over any distance so could in theory enable, for example, real time communications with a future Mars colony. It should also in theory be very hard if not impossible to intercept. There's no cables or wireless transmission between sender and receiver so nothing to intercept.
Definitely a fascinating field to keep an eye on.