We can only speculate about the lower bounds of compile times, but making things faster takes a lot of work. Rustc is a huge codebase, and making general leaps requires large architectural changes. We’ll just keep chipping away. It’ll take some time.

There has been a lot of progress, it’s just been slow and steady. For example, since the first of 2018: https://perf.rust-lang.org/compare.html?start=2018-01-01&end...