This feature is available in all versions of Consul Enterprise.
Consul Enterprise enables the capability of automatically upgrading a cluster of Consul servers to a new version as updated server nodes join the cluster. This automated upgrade will spawn a process which monitors the amount of voting members currently in a cluster. When an equal amount of new server nodes are joined running the desired version, the lower versioned servers will be demoted to non voting members. Demotion of legacy server nodes will not occur until the voting members on the new version match. Once this demotion occurs, the previous versioned servers can be removed from the cluster safely.