In all likelihood, somewhere down the line quantum computers will get more compact and I’m guessing could be packaged in the form of a GPU where it would plug into the PCIx slot on a motherboard. At the rate we’re going I would hope for 15-20 years in the future.
If we get to the point of being able to commercially ship Quantum Processors to consumers, I’d imagine we’d have solved the problems for quantum encryption, and created API’s for easier implementation in programs and games.
Also just because a quantum ray-tracing algorithm hasn’t been written, doesn’t mean it can’t be done.
Lets be real for a minute though, by the time quantum computers are commercialized, our general use CPU’s will theoretically have exponentially more transistors therefore speeding up renders, and allowing for higher render resolutions. We’d have to re-evaluate at that point to see if quantum computers could even provide any benefit over general computing.