I think a couple factors will come to play.
1. The mental component is gone now. So that's one less hurdle for a team to do it.
2. The NBA - one and done rule change could affect this and the current FBI investigation. The number of truly dominant top teams should disappear. This year there wasn't a dominant team. The other three games were all within 20 points where last year the 1 vs 16 matchups included blowouts all of at least 20 including 30-40 point wins.
3. Flattening of the second tier. It seems as if the lower tier is flattening more. There is more mixing of teams in rankings from the lower end to the middle end, so the weakest conferences might not suck as bad as they used to compared to mid-majors. This is elevating the level of play of the last 6 teams in, and with the first four, the weakest two #16's don't even play a #1. Since that change, the 6th worse team in the tournament is still a 16 seed instead of a 15 which UMBC would have been in the old system.
I think in general, a bad team has about a 1 in 20 chance of beating a good team on a given night. I'm going to guess around 5-7 years we'll see it again.