What happens to miners when proof of stake is rolled out phasing proof of work out completely?
ASIC miners must move to another ethash mined blockchain with the same parameters as Ethereum. However for miners using GPUs, they can move to any blockchain that GPU mining is efficient for. Alternatively the GPU miners can participate in something like Golem. Lastly, they can simply sell their GPUs. ASICs may be harder to sell when Ethereum stops being POW.