The flooding and inevitable destruction of the city is decades away. It's still abstract. Some people might even think it is preventable.
I don't think it's unethical to sell. People have their own motivations. Maybe a buyer just wants it for 5 years, who knows. Probably the risk will get baked into market price. What does need to happen though is the federal government needs to step up, because they're the only ones who can, and guarantee they will buy it for a certain percentage of appraised market value. I would imagine that percentage will decline over time until they declare the city a total loss, after which your property is declared worthless. If they do this now, they can make it possible for people to leave with some semblance of dignity and mitigate hardships.
This sort of puffery is relatively minor and is thus not tremendously unethical, but it is unethical.
what exactly is a lie in this context specifically I wonder?
Is this so difficult that you can't even detect your own lie specifically constructed as an example of it?
> Is it unethical for me to sell my Condo which is in “up and coming area” which never upped and never came and has a very high crime rate (with/without disclaimer)?
That would be lying in order to sell something, and thus unethical.
You then expressed confusion over what exactly would be a lie here, despite you very clearly stating what the lie is in the above quote.