The end of POW will be a difficult time for miners, because mining is a source of revenue.
It turns out that miners are not only miners, they are also crypto enthousiats, advisors and ambassadors of Ethereum for their social network. They have skills, and sometimes expertise in cryptocurrencies.
Stopping POW will create discontent among them.
I think it would be smart to involve as many miners as possible into the transition from POW to POS.
It means giving miners the opportunity to switch from one source of revenue (mining), to another source (revenues of validation).
Only a few miners will have enough Ethers to run a full node.
A solution would be to allow miners who have less Ethers to run partial nodes, that could be used to validate plasma chains, child chains, side chains …