WISP is very useful in rural areas. It's less compelling as an alternative to wired services in the dense urban environments where we'll see 5G deployments. You're going to have to run all that fiber, anyway.
I spent a decade on various WISPs, even had one of their towers on my house (free connection + cash = very yes). It was a city with a mix of single family homes on small lots and townhomes/condos. Cable doesn't exist there, so WISP was the way to go. It was pretty good until Netfix got popular. It was bad in the evenings when everyone would sit down and turn on a show.
Now I'm in a very rural place, lots of hills, thick trees. Luckily there is a telephone/internet co-op who put in fiber. I think they realized with the distances they have to cover that WISP and copper were out. I've never seen fiber to such remote locations.
We only have one cell tower that covers us now, so I won't hold my breath for 5G.