Back in 2010, 3D TV was so close to taking over the world it seemed like a done deal. Sales rose in 2011 and 2012 but then started to taper off. There were health issues; the technology was inconvenient - most types required you to wear special glasses - and 3D TV became the great new thing that never happened.
It will happen one day, but it is not a hot topic any more.
No, today's hot topic is driverless cars. The world seems convinced they are just around the corner. Share-tippers are working out who to invest in, and even who to short (car parks are down, Uber is up) and politicians are jumping on the bandwagon and passing the laws needed to make them legal.
But it is all too soon. Driverless cars are not coming. Yes, there will always be more and better driver-assist technology available, but then, we get new driver-assist technology all the time - it's nothing new. The big new thing of cars driving around UK roads with no people in them is not coming anytime soon. The technical and legal obstacles are just too big. Our roads are too jammed, too confusing and other drivers too unforgiving for a driverless car to work.
Driverless trains we already have; driverless planes are feasible, but cars - nope, not for a long while yet. For the time being, contrarians will be rewarded.