For me, the universe of TOS is and was the future. When I think of the future, I imagine it to look like TOS. I know that some people can't get past the superficial aspects of hairstyles, studio-bound locations, grainy special effects and what not. I think they should try to get past this stuff, because if they can they'll find other rewards. But if they can't, then perhaps TOS is not for them. But I think that because many of us first saw TOS when we were unable to see anything but the wonder, the romance, the adventure, and the endless possibilities, it buried itself deep, deep inside us and will never leave. I saw 2001: A Space Odyssey
around the same age (at a real Cinerama screen, no less), and it had a similar effect on me. So, that clean early/mid-1960s International Style aesthetic is my idea of what the future looks like. (That's also one of the reasons I like Mad Men
I also saw Lost in Space
about this same time, but, for some reason, that never looked futuristic to me. Maybe because, even at that young age, I thought LiS was just stupid.
The "Future" is a moving target. What you think is futuristic today might well look ridiculous in a very short time. Who knows what it will look like. Will it look like TOS? Maybe, maybe not. Maybe Steampunk will be the defining style of the late 21st century, and we'll all be wearing corsets and goggles. But it's fun to think about it. Hope to see you all in the future!
(Note: Part of this post previously appeared on another website)