You're assuming that this is going to be on some island or something. If we're talking about a major city in an expansion, the surrounding areas aren't all going to be tropical like Stranglethorn. You're more likely looking at a continent with various locales and environments, including the ones you describe above.
If we're going with this "Nightsquall" idea, then it's going to be a long established pirate location. Something akin to Port Royal, which was one of the largest cities in the Caribbean in its day, and it was created and controlled by pirates and privateers.
In the end, this is the most obvious hint to 11.0;
Thrall in the promo image.
This was the promo image prior to Shadowlands reveal;
And this was the promo image prior to BFA reveal;
If history (and Chris Metzen) is anything to go by, the next expansion is going to involve Thrall in a high capacity, since Shadowlands heavily involved Sylvanas, and BFA heavily involved Jaina.
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So seafarer means pirate now? The Kul'tirans are literally a nation of seafarers.