I don't think they are getting old. It might seem so because the only games that come out are situated during the second world war. Maybe some other ones in other places in history, but history itself has had so many moments and things happening. We just haven't seen any games throughout different stages of history. And that's why I don't think it will ever get old. Of course just as other people mentioned, sci-fi can have much wider possibilities, but still historicly based games are very good in my opinion.
