I'll talk about one of the reasons AI is difficult to predict.

We have some ingrained bias's about what is easy and hard for an intelligent machine. However, the way AI progresses does not follow those intuitions. For instance, in the 90s we were able to make a chess computer that was able to beat the best chess player in the world. It was until relatively recently that if you took all the chess pieces and threw them into a trash can, and ask a robot hand to set them up correctly on a chess board it was able to do it. It was like a 20-year gap between AI being the best at playing chess to being able to setup a chessboard.

This is not intuitive at all. I remember pretty recently reading art was going to be one of the last things AI would be able to do. Turns out we were pretty close to good text->image. It's going to be really hard to predict the path that AI takes. Problems we think are hard are going to be easy, and problems we think are easy will be hard.