The one I'm saddest didn't come true:
Prediction #22: Store Purchases by Tube. Pneumatic tubes...
Prediction #16: There will be No C, X or Q in our every-day alphabet.
The one that should have been:
Prediction #17: How Children will be Taught. A university education will be free to every man and woman.
It is surprising how many came true! And not a single prediction about Batman!