Is 2016 Winnebago Journey prewired for brake controller?

Probably. If there is a wire on the correct pin in the plug, it’s likely wired.

The one in my Fleetwood was buried.

Brake wiring using the typical electric brake controller under the dash always uses a blue wire going back to the trailer hitch to connect to the towed vehicle. If you see a stray blue wire under your dash, or back at the hitch, then it's probably wired for it. It's always best to check the diagrams for your model of course.

Here's a pretty neat trailer wiring diagram covering all the standard connectors that might be back near the hitch: Trailer Wiring

You could go to the Winnebago website to the Manuals and Diagrams section and download the wiring to see if it is wired.