The efficient-market hypothesis implies that housing prices in South Florida are lower than they would be if sea level were guaranteed to stay the same.
And nothing in the article contradicts that.
In other words the downward pressure from the prospect of sea-level rise is probably being cancelled out by upward pressure from other factors -- e.g., the fact that Miami is an important nexus of flows of money and talent from and to Latin America.
1) In addition to there being many non-monetary factors in a housing market, as hollerith mentioned, housing markets are also generally not very efficient compared to others.
2) Any bet that land prices will plummet for this reason (this is something a hedge fund would do) would have to calculate the 'risk' of massive intervention when/if the problem gets to the unignorable/still-fixable-even-at-enormous-cost stage. If presented with the choice of "evacuate south florida" v. "here's a very costly plan to save Miami," I think America would choose the latter.
I live in Amsterdam, and I've (apocryphally, quick googling didn't reveal the number) heard that over the centuries the Netherlands has spent ~1 trillion inflation-adjusted dollars on its water management system. "Rationally"—and very simplistically—speaking, these people "could" all go live somewhere else, but that's not how the world works. (Nor should it, IMO, but off-topic)
My understanding of the situation is no one has even proposed a "very costly plan to save Miami." This is Venice on an accelerated time scale. Miami pales in comparisons proportionate wealth and power when Venice started sinking in earnest.
I'd be very reluctant to short Manhattan real estate because protecting Manhattan from higher sea levels is merely an engineering challenge and affordable relative to NYC economic output. Manhattan is basically made out of granite. South Florida on porous limestone.
And nothing in the article contradicts that.
In other words the downward pressure from the prospect of sea-level rise is probably being cancelled out by upward pressure from other factors -- e.g., the fact that Miami is an important nexus of flows of money and talent from and to Latin America.