Isn’t that kind of like saying that “I promise that I won’t shoot you again.” But simply stabbing the person with a knife later?
I take it more as a promise that God won’t do something again that would eliminate the vast majority of the population, the flood was just a means to an end.
You can interpret it any way you want. The Book of Revelations makes it quite clear that there will be an end to the world, and that a large number of people are going to die in the process (and most of that in the prelude to the Rapture).