Ether developers are going to perform a hard fork in order to implement Proof of Stake.
The developers see POS as a technology that will scale far more effectively than POW. They see POW as a limited technology.
The planned update is called Constantinople which is designed to transfer Ether from Proof of Work to Casper Proof of Stake.
Proof of Work means that real physical machines must use real world power to process transactions in order to maintain the network. As it becomes more difficult to mine a miner needs more hardware and power to keep up with the network. This is considered ineffective.
One solution that has not been considered is building Proof of Work technology that operates off grid such as solar power, air pressure, wind or a combination. If something as simple as a calculator can be powered by a solar panel then why not build mining equipment with the same attributes.
The technology that would be required would need to generate more electricity but it can be done. POW is more secure than a POS virtual network since it is physical hardware owned by different people who monitor and maintain the machines. This gives the network multiple physical locations which makes it harder to take down the network.
There are far less obstacles to build a physical miner which means anyone can secure the network. It is the network of the people by the people.
Proof of Stake is when people lock a certain amount of Ether in order to process transactions virtually. This means that the network can be maintained with far less resources.
Ether is locked away not just to virtually mine but as collateral for if anyone chooses to attack the network they will lose all the Ether they have staked.
When Constantinople is implemented it will make it unnecessarily complex to produce blocks using POW.
The developers have done this because they likely do not have the approval of the miners to fork Ether. It seems the developers hope that by making it more difficult to mine Ether the chain will be killed leaving the POS chain as the lone ETH survivor.
By forcing out the miners developers believe that the Ether community will have no choice but to use the new updated chain there by giving the new chain liquidity.
The justification for these actions is the improvement of Ethereum. There is no need to attack their own miners but yet that is what will happen when Constantinople goes live.
There are 3 possible versions of Constantinople that were debated which are EIP-1234 will cause a reduction of 2 Ether block rewards, EIP-858 is designed to reduce current block rewards to 1 Ether, and EIP-1295 will not change the block reward but instead will make it more complicated to create blocks
. After much debate it was decided that EIP-1234 Difficulty Bump would be implemented.
This is one step closer to the Ether Ice Age.
Either people will simply mine another cryptocurrency or they might dig in their heals and improve their hardware. The one thing that is clear is that there are plans to leave miners out in the cold.
Sources
https://github.com/ethereum/EIPs/commit/7dbcbc35e4fd859a3d2b5b5c51bee805beaee42f