Getting into the LN thing, every answer opens up a new question... so you have to tie an amount (from single address) to a establish a channel. Sort of staking? I can see how this can work for regular large payments, say with an exchange, however its a big ask to expect people to do this for small payments. It seems like putting up a credit tab with the shop/bar and you have to hit a minimum spend to make it worthwhile.
You can route payments through people, and have payments routed to you through people. You don't have to just transact with the other person in the channel.
The cost of on-chain transactions will likely increase.
In the short term on-chain transaction fees will likely decrease. In the long term, if more people use Bitcoin, fees will increase, but less so to levels that they would be without LN.