It's not just rising sea levels. Natural disasters will continue to increase both in terms of frequency and severity. Less steady rainfall, more aggresive cycles of drought that kill your crops and floods that destroy homes and businesses.
Some places are going to lose their sources of drinking water and others will face deadly heat. Either way millions of people are going to get displaced every year.
Yes, but I guess that some people could pedantically argue that a human kind of one billion people living only in a few acceptable areas will have a median standard of living much higher than a human kind of eight billion people spread all around the world. After all, all those millions of displaced people are going to die of old age and their pains will go away with them /s Sarcasm apart, we don't really care much about the pains of the people who were displaced millenia or centuries ago. That's history.
The point of view changes according to the sets of people one belongs to while still being alive, eg living in a warming Denver or attempting not drown in NYC?