Don’t know if this counts, but the old Dick Tracy strips had gadgets that were considered futuristic, but were used in present-time context.
Like the ever popular Two-Way Wrist Radio, which predates teleconferencing. A 1930’s strip had a telephoto machine which predates the fax. And of course, they had those one-man jet cars that looked like giant salt shakers.
Frederik Pohl’s autobiography The Way the Future Was has The. Best. SF. Title. Evah! 
Not much in it about predicted technology that never happened, but very interesting stuff about SF fandom - and real life - in the 30s, 40s, and beyond.
Maybe one of your panels can talk about why zooming off to Jupiter to found colonies on the moons would NOT work, because of things we’ve learned since the 50s such as radiation belts, sulfur volcanoes, etc.
You could have a panel about missed predictions. 50s sci-fi had home robots, flying cars, daily trips to Venus, but did not have the Internet. So the future oriented community missed: Google, Wikipedia, Blogs, YouTube, flash crowds (Niven came close!), Spam, Phishing, SDMB, etc. We may not have robotic replacement body parts, or “Transplants R Us”, but we have non-invasive medical imaging (CAT, PET, MRI, ultrasound), endoscopic surgery, blood tests for heart disease, pills for just about everything, TV ads for the same pills, etc.
How about Escape from New York, where Snake Plissken paraglides to the top of the abandoned World Trade Center?
I’ve vaguely heard some meme to the effect that the Eugenics wars happened secretly and no one noticed. Is this a joke or a serious ST retcon?
Dave Szondy’s website Tales of Future Past is an excellent guide to this subject. With lots of classic movie stills and pulp-cover SF art! 
There is actually a purportedly serious field of study, known as Futurology or Futures studies, which aims to predict the future in broad outlines. Its predictive success to date has been limited, AFAIK. There are just too many imponderables – especially WRT scientific and technological progress Who in the 1950s could have predicted the possibility of the silicon chip – or its social effects? Who can, today, say with confidence whether we will ever develop effective nanotechnology, strong artificial intelligence or direct neural-electronic interfaces? Any of those might be The Next Big Thing, or it might be as sure a dead end as perpetual motion.
What year is Metropolis set.
It would be interesting to divide it in to decades the predictions were made. What sort of future did the 1920’s see, the '30s. etc.
Wikipedia doesn’t mention anything about its being a secret/unnoticed.
I just watched it again recently. IIRC, they use the standard trick of just adding 100 years to the present date, which would put it at about 2025.
Wim Wenders’ Until the End of the World, made in 1991, set in 1999.
At the time, a friend of mine recommended that movie as the best-imagined near future that he’d ever seen. A character uses a pay phone with a video screen, but it’s a public phone so it looks scratched and used. There are futuristic cars on the streets, but some of the current (as of 1991) ones as well.
I finally saw it in 1996. I could see what my friend meant. Its version of the future was still familiar, and it looked like real people lived in it. Lots of movies get it wrong by being too pristine and sterile.
I know a lot can be done with makeup, but wouldn’t it have just been simpler to get Julie Newmar?
I have an anthology called The Year 2000, done about 30 years ago and set in the year 2000. I can’t find it at Amazon, at least not among all the other books with those words in the title. If you’re interested I can send you complete information on it when I get home.
Childhood’e End had the first moon launch in 1975, which seemed to be the consensus date before JFK moved it up. That’s about the one sf event I think we beat.
I’ve got lots of books and reference works, as well as a pretty complete set of magazines from 1960 on forward (and most of the ones from the '50s.) Let me know if you’re looking for something in particular, and I might be able to scan it for you.
[airplane ii: the sequel]
TED STRIKER: But we’re not living in the past any more. Or the present. This is the future.
[/aii:ts]
YOYODYNE: Bringing you the future tomorrow!
nitpick – Actually, no, none of them are, because none of the violate the laws of physics. They may be dead ends, but it is reasonable to think they might work out in time. Not so perpetual motion.
I think the point of robot Julie Newmar is programmable Julie Newmars. En masse. With a weapons system like that, who need nukes?
Serious. There was a two-book series about it. Gary Seven was involved as well.
If no one noticed, how did anyone know about it later? 
I am definitely interested.
This may be a topic for another thread, but are there any dates we think of now as being a shorthand for “The Future” likein the year 2000 ? (or 1999, or 2001?).
2020? 2050? 2099? 2100?
No oomph for me. Sounds like just rattling off random numbers. Not like . . . the year TWO THOUSAND
There’s the long running British Sci-Fi comic 2000AD
And of course Gerry Anderson again