For example right now who knows which one of: VR, crypto, biotech, etc will be the “big thing” of the decade? If one trust the power law one will still dwarf the others by its importance in retrospect.
Sometimes you know the next big thing, but tech has to catch up. I knew in 2003 that smartphones would be huge. I was a big fan but I knew not everyone had unlimited data plans like I did. Also the UI was clunky. There was no question that with an improvement in tech there would be mass adoption. There is no question that self-driving cars or electric cars will be near universal at some point. Whether that is 10 years or 50 years is the only question. Cryptocurrency too is just waiting for some killer application or a major bank crash before people say yeah this is the way to go. I think we know many of the next big things now, we are just waiting for tech (or people) to catch up. My daughter, for example, is 9 and I don't think she has ever touched a physical light switch. She grew up in a house with 17 Alexa devices and 70 smart switches, outlets, and lights. You just tell Alexa what you want. At some point in the future the rest of the world will be living the way I do now.