I think that after this the price of ETH will increase very much. Otherwise, mining ether will simply die.
In reality, ETH price fell considerably today.
Additionally, I believe that miners will switch to other options, such as Ethereum Classic, Callist Network, and so on for their mining works.
The switch to PoS of ETH will not affect them at all.
Ethereum Classic just had 51% attack... so don't think people will mine ETC, ETC does not even look like a good option without this issue. Lower block reward will affect mining, how much? Time will tell.