Life Cycle of Sci-Fi
One of the problems when writing a science fiction story is that real science and technology leapfrogs your imagination, which of course is generally a good thing (only very rarely do things turn out to be as world end-y as we thought). Think of communicators in Star Trek TOS, or the talking computers. Of course the computers in Trek seem very primitive to us now, even it’s supposed to be set in the 23rd century. Another thing that can happen is the theory or idea you based your speculative fiction on gets proven to be complete nonsense by some smartass in a lab coat. So what happens to it then? Does it become worthless? Are the secret cabal of sci-fi authors who sabotage real science experiments and have done all in their power to prevent news of actual alien contact getting out, justified in their fear that if it does people will stop wanting to read about fictional ETs?
I don’t think so, necessarily. If the stories are still entertaining they might become fantasy or steampunk or the like. Or they become a document of the kind of anxieties and fears that society had at the time. All those atomic monster movies from the fifties, for example, reflecting people’s fear of nuclear power and annihilation (Godzilla being the most well known). Or indeed the hopes and dreams they had, as in Star Trek.
Science can fuel the imagination of writers and open their minds to all sorts of new possibilities. So long as there’s a still a good story as well I don’t think you really have to worry about becoming dated. After all, we know a lot of our old myths probably aren’t true, but they still entertain and we keep retelling and reimagining them.