I suspect we're not likely to run into the problems described in https://github.com/etcd-io/etcd/issues/20967 because we don't see a lot of clusters that replace control plane members but it'd be nice to pick up the fix for that in 4.20.z and 4.19.z so that we can reduce the risk of issues in clusters that upgrade to 4.21 and later. If we do that ahead of 4.21 GA date we will also bump the minimum version of 4.20 to get to 4.21.