That would depend on your idea of ‘over done.’ While Science Fiction started with the glory days of the space opera, things have changed over the decades. The idea of the world not being a pretty place in the future is something presented in many novels. Is it right? It is wrong? Totally depends on your viewpoint of how the world’s advancing. If you ask me, the dystopian future is more likely then a positive one.
With that said, should Sci Fi writers shy away from it? No. Any idea can be ‘over done’ depending on the person involved. In all honesty, there’s no real original ideas left anyway and we all borrow from other people when we write. However, that’s neither here nor there.
What matters is your viewpoint on things. If you believe in the ‘Blade Runner’ type future then by all means write a book that fits what you see. Don’t worry about what others think! You the writer have to write the story you have in mind and then make it commercially viable-not the critics. Keep that in mind when writing and learn to ignore the artistes.