The Ethereum Foundation announced the deprecation of testnets such as Ropsten, Rinkeby, and Kiln, but users and developers still have time to complete the migration before a complete shutdown. Specifically, the Kiln Merge testnet will shut down shortly after the Ethereum mainnet transitions to proof-of-stake.
Ropsten has transitioned to Proof of Stake and will close in Q4 2022. Rinkeby is a geth-based proof-of-authority testnet that will not transition to proof-of-stake and will close in Q2/Q3 2023.
It is reported that the measure is designed to encourage users and developers to migrate to Goerli or Sepolia as soon as possible to test Ethereum in the combined environment. After the merger, Rinkeby will no longer be a suitable test environment for the Ethereum mainnet.