The community leader of the Ethereum Foundation, Hudson Jameson, has confirmed that the Instanbul Hard Fork will be released on December 7, 2019. The exact timeframes may change due to variable block times. Ethereum node operators should update their nodes before December 1, 2019 to include variable block times. Users can track the progress of the upgrade online using the Ethernodes tools and receive a real-time status of preparations by miners, exchanges, developers and nodes.
In addition, the official announcement included a list of final versions compatible with the Istanbul upgrade. In addition to Geth and Parity, some exotic implementations such as Aleth, Besu and Nethermind are included. The announcement also included a warning. Once the update is done, if a user is using an Ethereum client that is not up to date, the node client will be synchronized again with the pre-fork blockchain. This block chain is not compatible with the new Ethereum and cannot send ether nor work in the upgraded Ethereum network.