So yes, I realize this a joke map (honestly, a giant, probably mostly freshwater sea, in the US would be a blessing). But what you’re describing is the main issue with climate change.
It’s not going to be “the day after tomorrow”. It will be coastal cities… which are… like nearly ALL of them… losing all their economic value. In the US when having this conversation I say “what do you do when any building in Manhattan is uninsurable? What do you do when it’s sure to have severe damage?”.
For most people there are plenty of places to go, but the “going” is going to be very, very ugly.
Not as great as it seems. The thing is, everyone’s retirement is tied to real-estate. The numbers my vary country by country, but nearly all pension funds and mutual funds have significant exposure to real-estate that is just ignoring the issue that those properties may become uninsurable. That’s before what happens due to the economic disruption of all those cities slowly, then at an increased velocity, relocating.
It’s not going to be pretty.