I don't really subscribe to the whole if civilization collaspes there will be no technology in anyone's lifetime again thing. You aren't going to go back to ordering shit off amazon from your smartphone or anything. However the knowledge that things like refrigeration, radio transmission, internal combustion engines, water treatment and such are possible is going to drive people to eventually find out how to get it by any means necessary.
How quickly this happens is a question of whether the majority of people adopt a "technology is too dangerous/a sin against God" idealogy or not.
The only disadvantage of display port that I can think of is that it's harder to find capture devices (or at least Linux compatible ones) that have display port. Generally no one cares about that stuff though. I use capture cards because I sometimes do stuff involving other computers and it's 1000 times more convenient to have a vlc window floating around with the display output.
No one seems to have this use case besides me, I'm just glad that there exist capture cards fast enough to do playback in real-time and not a 5 second delay. I don't stream.