Gradually, then suddenly

There's a passage in Ernest Hemingway's novel The Sun Also Rises in which a character named Mike is asked how he went bankrupt. Technological change happens much the same way. Small changes accumulate, and suddenly the world is a different place. Throughout my career at O'Reilly Media, we've tracked and fostered a lot of "gradually, then suddenly" movements: the World Wide Web, open source software, big data, cloud computing, sensors and ubiquitous computing, and now the pervasive effects of AI and algorithmic systems on society and the economy. What are some of the things that are in the middle of their "gradually, then suddenly" transition right now?