No, direct mount rim brakes wont make some huge comeback. They were a short lived answer something that very few people asked.
20 years from now, most bikes will probably be electric. Heck, most cities may not have clean enough air to ride. Or some may be underwater. Some may be riding on another planet at that point, which introduces all sorts of issues when it comes to tire pressure and gear ratios.
I dont know whats to come, but I do know direct mount rim brakes arent the answer to that unknown.