Isn't steampunk essentially science fiction that's set in the past, near the industrial revolution?
I predict that once the Information Revolution is over, and the next one has begun, there will be people writing fiction set in an exaggerated, magical caricature of the early 2000s.
But what about the present day? The technology that we might think of today as thing of the future might just be developed in some obscure lab today, or 5-15 years ago. Wouldn't it be fun to speculate in that direction?
Going backwards just a little in time... Dieselpunk is often set between the two world wars. I loved the style of The Rocketeer, Skycaptain and The World of Tomorrow along with other post-aviation, pre WWII sci-fi/fantasies (even if the non-stylistic aspects of Skycaptain were deeply disappointing).
There's definetly a point, though - Have you read Sci-Fi set in the time of the Pyramids? In the time of the Roman Empire? Would you? What would change?
It's worth looking up "Rome Sweet Rome", a short story that got some acclaim a few months back when it was written on Reddit and then optioned by Warner Bros. It's modern military sci-fi, essentially, but the setting and the detail that's put into "What would happen if a modern platoon were set down in the time of the roman empire?" is pretty good.
In the meantime: http://www.ams.org/notices/199805/review-graffi.pdf
Card maintains that switching genres wasn't a difficult
thing for him. He believes that, ultimately, the
difference between the two genres is largely on the
surface. "Half joking, I was writing to Ben (Bova) about
this very subject, and I said, look, fantasy has trees,
and science fiction has rivets. That's it, that's all
the difference there is, the difference of feel,
perception.Just off the top of my head I can think of: Conrad Stalingrad, Jainsiaries, and 1635 (Eric Flint).
And there are ofcourse the alternate history stories like the Drakar chronicles (wherein there was a African slave-state empire rather than traditional colonialism).
Michener's novels? (How does "past sci-fi" differ from "historical fiction")
Alternate history novels like Fatherland?
Anathem takes place on another planet, and in our future (in that characters in the book have our present as their past).