I almost agree with your assessment but my conclusion is quite different.
I believe we will see dramatic sea level rise (multiple meters) in my lifetime. The IPCC forecast is way too conservative and does not take into account recent scientific data that the ice in Antartica and Greenland is melting much faster than previously thought. The trends pre-2010 are irrelevent; it's only since then that the oceans have finally absorbed the heat caused by the doubling of CO2 in the atmosphere, and risen in temperature (about 1 degree C), enough to trigger massive runaway ice melt at the poles.
This means much of Negril will be underwater at some future time. And more importantly, much of Miami, New York, Mumbai, Shanghai, Lagos, etc. I think that'll happen soon (by 2050). Most people think it'll take longer (e.g. by 2100), But we will get there.
You are correct that by the time that happens the Jamaican economy will be in shambles. However what you seem to be missing is that the world economy will also be in shambles. So then the question becomes, where do you want to be when this collapse happens?
I claim that you do *not* want to be in New York. Or Miami. Or London. Or Toronto. Or any other large city that Jamaicans go to when they "go foreign". People in big cities will starve. Money won't protect you after the world economy collapses.
You'll want to be somewhere you can live in safety and grow your own food.
I think farmland in rural Jamaica is an excellent choice. Maybe not perfect, but for me the best available choice. I know people who are looking at New Zealand for the same reasons. For me that's too far and too expensive.
Oh dear, I've shown my hand as far as how I'm thinking about my future and my motivations. Now you'll all think I'm a nutcase.
Well, at least I'm not moving to spend my remaining years doing drugs and chasing prostitutes. Growing vegetables is better, eh?
Peace and love,
Richard