Just like previous halving, some miner will stop their mining activity and sell hardware they no longer use while other's will continue mining with lower profit.
In theory, at a certain point difficulty will drop and mining will go back to being more home miner friendly, but that is decades in the future.
I think you're overestimating LN as scaling solution. People who rarely make transaction (usually investor and holder) wouldn't bother use LN, unless they're willing to "lock" their Bitcoin on LN channel.
Possibly, or more people are going to keep their funds in their own wallets and then put them into massive LN routing services and use their wallets. Knowing they are not secure but neither is the cash in your wallet. So you keep your cold funds cold and your hot funds in a very insecure way, but not enough to matter.
Once again time will tell.
As others have said this topic keeps coming around, but rehashing it now and then might not be the worst.
I also see other coins imploding messily as their only reason to exist is for people to mine, make a quick profit and dump and leave. As more of those go away I can see some people running a 'low power low noise' miner at home to make a few dollars.
-Dave