My understanding is that (at least right now) most Quantum Computers are equivalent to ASICs; they are custom-designed to solve specific problems, or problem domains.
Quantom computers aren't replacing classical ones in the foreseeable future. At best, they will be simmilar to GPUs (and even that is a stretch).
At least this is true right now but the above could easily turn out to be one of those "None will ever use more than X bytes of ram" quotes.