Comment 2 for bug 1915722

I don't know for sure, but looking at https://hg.mozilla.org/mozilla-central/log/9cf59af57183/taskcluster/ci/toolchain/rust.yml, in the past year there have been as little as 12 days (for rustc 1.39) between the upstream builders were upgraded and the version became a hard requirement. In other instances (1.47), the lag was longer (1.5 months).

I wouldn't bet on it, but I think it's safe to say that we have somewhere between a couple of weeks and a month before this becomes urgent.