This is what's being accomplished by one amateur with a little bit of hardware. Imagine what will happen when you have professional services (legal or otherwise) making altered videos of whoever or whatever you want. Want court evidence of your wife cheating? Fake grainy hidden camera video. Want to discredit a politician? Here he is picking up a male escort and using racial slurs. These sorts of things could be used…
With a few obvious exceptions -- like one particular shot of Ivanka's face that crosses the line from realism all the way past comedy into horror -- some of these replacements are almost good enough to start fooling people. Voice synthesis is approaching the 'solved problem' point as well (e.g., https://www.youtube.com/watch?v=YfU_sWHT8mo ). Not there yet, but getting there.