You do have the ability to download specific versions of the swift toolchain. The Swift website has instructions on how to install them and they’re also available on the GitHub releases page.
I am proposing an RFC process to upgrade swift versions. I’m not entirely sure how often we’ll do the upgrade but if the audience remains small then I think we can upgrade more aggressively than the rest of the LLVM project upgrades other tools (e.g. CMake, Python).