If Ben Evans doesn’t know (and he doesn’t, really), then nobody knows.
In 2000 or so, when I was a baby telecoms analyst, it seemed as though every single telecoms investor was asking ‘what’s the killer app for 3G?’ People said ‘video calling’ a lot. But 3G video calls never happened, and it turned out that the killer app for having the internet in your pocket was, well, having the internet in your pocket. Over time, video turned out to be one part of that, but not as a telco service billed by the second. Equally, the killer app for 5G is probably, well, ‘faster 4G’. Over time, that will mean new Snapchats and New YouTubes – new ways to fill the pipe that wouldn’t work today, and new entrepreneurs. It probably isn’t a revolution – or rather, it means that the revolution that’s been going on since 1995 or so keeps going for another decade or more, until we get to 6G.