This is a common fantasy among technologists (and a common fear of teachers) when confronted with educational technology. But it won't happen in our lifetimes. It will not be possible to replace teachers with technology until we discover true artificial intelligence.
Educational technology, correctly applied, can be a force multiplier for teachers. So it may mean we can teach more students with fewer teachers. But it also means that access to education will increase (which may cause demand for education to increase).
One way or another, someone will always need to be available to answer students' questions. Books, videos, and clever programs running in web browsers simply can't do that.
> One way or another, someone will always need to be available to answer students' questions. Books, videos, and clever programs running in web browsers simply can't do that.
Can't we use a model similar to Stack Overflow for answering students' questions? Most questions are bound to repeat, so I don't think there would be so many questions for the experts to answer after a while.
I've been teaching people to code for 20 years. In virtually every course I've ever taught, at least one person comes up with a question that I've never heard before. If that person were limited to learning from a web site or a video, that's the point at which that person would get stuck. But because I can answer their question, they can continue quickly.
Learning from books by yourself is one of the most inefficient ways to learn. This is particularly true for technologists. Very few professionals learn their fields very well in a vacuum -- it always struck me as absurd that software engineers are expected to do so.