We are just waiting the next develpoment in key tech, mass production is behind a few aspects like... not requiring mK temperatures and better interconnect to use the actual quantum bits.
Current CPUs have billions of transistors but only thousands of pins for input/output, that's one issue we'll have to solve before big quantum chips become useful, maybe optical communications to reduce power?
Timeframe? Couple decades to 50 years, but I bet more on lower side given the current pace of improvements, even after the relative slow-down with silicon scaling.
Punch cards, vacuum tubes, transistors, micro-chips... next!