4.8 CVO adds a new precondition, similar to its existing Upgradeable precondition, here, that looks at the etcd ClusterOperator's RecentBackup condition when considering a desiredUpdate bump:

• If it is unset, the check should fail, and that failure will be reported in ClusterVersion's Upgradeable=False.  We should ensure the CVO polls any failing checks, and maybe some successful checks, so users don't have to kick us to get us to notice things like RecentBackup being set.
• If it is != True, the check should fail, and that failure will be reported in ClusterVersion's Upgradeable=False.  We'll pass through the etcd operator's reason/message, so hopefully the pending case gets a nice message like "Waiting for an etcd snapshot to complete, should be ready in a few minutes." that keeps them from feeling worried.
• If it is True, the check should pass, and assuming the other checks pass, the CVO accepts the update and starts in on the new version.