The miners don't need to switch; in fact, they can't. There's no mining on the PoS network. Miners will effectively have to stay on ETH1 or move to another cryptocurrency.
I think it's largely political, getting stake pool nodes and people using ETH2. There will likely be ETH1 and ETH2 running side by side for some time. ETH1 can be burned to get ETH2, so there's a one-way transition (though I'm not sure if this story is complete yet, that's the plan anyway).
I wonder if we will have a new wave of miners. If you want to get in, instead of spending $10,000 on mining gear, spend the same amount on coins which are easier to sell off later when you want to get out.
Staking income is much lower than mining. Eth 2.0 is targetting a 7% annual return, outside of any currency inflation. So there will be stakers, but it won't be the gold-rush of mining.
I think it's largely political, getting stake pool nodes and people using ETH2. There will likely be ETH1 and ETH2 running side by side for some time. ETH1 can be burned to get ETH2, so there's a one-way transition (though I'm not sure if this story is complete yet, that's the plan anyway).