I wouldn’t put that as an absolute:
My over/under is 2099, and I’m going with the under.
Good point.
But they moved. Said another way, the old town was abandoned and a new one was built elsewhere. Perhaps with some subsidy paid to some folks, but surely not 100% of their costs.
The USA will not be able to abandon every coastal town from Brownsville TX to Boston MA. Although they all will deserve abandoning. So lotta folks are going to be living in a lotta these collapsing infrastructures.
They will try very hard to protect NYC and maybe DC. They will both end up with storm walls and who knows what else.
The subway systems will be pretty vulnerable. Even Superstorm Sandy showed that.
Florida will be the most devastated IIRC.
Somehow I just don’t see NY being as romantic as Venice. LOL
I’m not readily pulling up a useful topography map. Wondering how far “inland” it might be worth relocating.
Found this list of the elevations of major US cities.
If NYC and DC get inundated a couple of times, rather than pricey attempts to insulate them, it might make sense to relocate operations to Atlanta or Pittsburgh. The major Midwest cities and most of Texas will remain high and dry.
Not sure what it would take to move ports “uphill”…
This is slightly tangential to the thread, but it’s a cool resource for those interested in seeing the projected impacts for various areas. Sea Level Rise and Coastal Flooding Impacts (Miami is an interesting one to look at to see how the inundation changes at 1,2,..,10 ft of sea level rise - turns out at 10 ft, Miami becomes the new Florida Keys?).
What’s harder to guess is how much the inundation of these areas will have knock-on effects. Obviously not great for real estate prices in these areas, but what (if any) critical infrastructure is at risk over the next couple decades and ~1-2 ft of SLR? How much will it cost the local economies as these people are forced to move? 
If it were just SLR, I don’t think I’d be as concerned as I am about the time remaining. But unfortunately it’s also floods/droughts/storms/wildfires/extreme heat spread across most of the globe, and the economic and political chaos those will create as the costs accumulate.
This is my prediction as well. However, we will learn to cope.
As they say about bankruptcy - first it happens slowly, then [very] quickly.
Climate scientists are mixed on this. Some think that heating will stop almost instantaneously once we completely stop emissions, because the natural sinks are still not at equilibrium and so will immediately start to take out the extra carbon.
I am not sure myself, since the ocean hasn’t fully stopped heating up under current GHG concentration, meaning it would still continue to warm up, plus who knows if the ice-albedo feedback and anthropogenic but not directly consumption-based emissions such as wildfires would continue to add to the atmospheric GHG.
We are almost certainly not at equilibrium for the emissions we’ve already released. So there would still be some continued warming even if we stopped today. How far it extends beyond that is a very complicated question because a lot of the sinks as we currently understand them are faltering (e.g. the Amazon was a net emitter last year due in substantial part to land-use change by the people living there). If we stopped now, some might rebound (the Amazon likely if we left it the hell alone) while others (almost certainly for coral reefs, maybe/soon for the Greenland ice sheet) will continue to fail.
It’s also something of a moot point since we’re still increasing rather than decreasing our emissions even for the “simple” sources like the electrical grid. We don’t even have good answers for how to transition things like heavy industry as far as I’m aware, let alone are we in a position to actually cut everything over at scale.
Net-zero looks like a pipe dream at this point absent some techno-wizardry that can remove upwards of 40 billion tonnes of CO2 & equivalents from the atmosphere annually.