Agreed, but when the water comes up, they'll have to deal with it - either through construction or relocation or both.
Let's say that tomorrow, scientists make a huge discovery that completely changes the climate models. It turns out that not only is mankind not responsible for climate change, but it is indeed fluctuations in the sun. How does this change our mitigation efforts? The answer is that it does not. Either way, we have to respond to higher water levels and a warming climate.