If we take the C programming language, and one created last year, which one would you expect to still be used in 10 years? You can do this comparison for any two things where there is no inherent end date.
That's a different thing altogether. Because it does not take in account market adoption. If C was a language on life-support with no major project using it, it could be as old as hell but I would not bet on it to be around and useful 10 years from now.
Also, that saying is stupid because it makes it look like you can predict the future of technologies by using a single factor, while reality a rich, multi-dimensional set of problems.
Given a random sample of any thing at an arbitrary point in time, on average it will be in the middle of its lifetime. Something that is X years old will on average, continue for X more years. Of course, additional information lets you refine that estimate considerably, but it is mathematically sound and surprisingly applicable to everyday life (e.g. using a single serial number on a product to estimate total production).
The thing is, we typically have a lot of context for every technology we discuss, so bringing back this saying that reduces everything to one-dimension is just silly.
If you are truly an expert, you have a fighting chance. As a human, that means you are limited to a tiny number of specific subject matters.
horses for carriage seem to defy that kind of assumption
Gotta love these kind of sayings that have virtually no connection with reality.