When will Ethereum Merge to Proof-of-Stake?

This is a market group on when "The Merge" will occur on the Ethereum mainnet as described in EIP-3675 (or any successor to EIP-3675), transitioning the Ethereum blockchain to proof-of-stake. Note that forks to the execution layer and the consensus layer implementing EIP-3675 will not have any impact on the market resolution. Only the actual occurrence of The Merge will be considered.