We don't have Khan, but we do have Putin and his fellow autocrats around the world. Aside from not being genetically engineered, they aren't all that different.
Back around 1991, I read a book called Generations by William Strauss & Neil Howe, scholars who proposed a sociological model that American history followed a cyclical pattern of four repeating generational stages every 80 years or so -- a period of massive crisis and upheaval (e.g. the Depression and WWII), then a rebuilding era that's both more optimistic and more strict (e.g. the postwar boom and the Red Scare), then a generation that rebels against the strictness and experiments with new philosophies (e.g. the '60s-'70s), then a more self-absorbed, directionless generation that fails to address society's problems and allows things to build up to the next crisis period. I've found that everything that's happened in the world since the book came out has conformed pretty closely to their model, including the rough timings of events. So I've been expecting for a long time that things would build up to a crisis era like we're facing now, though I'd hoped it wouldn't get as bad as it has. But I'm optimistic that we'll come out of it relatively soon (since it's been 80 years since WWII ended) and have renewed prosperity in its wake, though not without further problems.
Maybe Star Trek is a future where people have learned from this model and use it to anticipate and prevent the worst problems. (Although the authors never claimed their model applied to anything but American history and sociology. Still, American and global affairs are pretty closely entwined these days, though that might be starting to change.)
