Casper/PoS: Stage 1
The full migration from PoW to PoS is expected in the next 1 to 2 years. The implementation of Casper will take several steps. In Stage 1 Ethereum will transition from pure proof of work to hybrid PoW+PoS and this stage is probably close to be finished. Stage 1 implementation includes two parts:
1. An implementation of the “fork choice rule”, the function which determines what the “canonical chain” is. This is the replacement for the “longest chain rule” in PoW.
2. A daemon (or integrated software package) that implements the logic needed to be a Casper validator.
All of the PoW-Mechanics will continue to exist and PoS-Mechanics will be added. Please find further information about the Stage 1 implementation in the Casper Version 1 Implementation Guide.