K's started going up a long time ago, as soon as teams were all realizing the value of OBP, generally working deeper counts, and the fact that an out is an out. three true outcomes, Adam Dunn, etc. it MAYBE was taken a bit too far (or maybe the playing field just leveled out because everyone was doing it).
a sort of course correction seems to be happening where (and i have no idea what the actual data says, so i'm talking out of my ass to a large degree here, to be clear) contact is being valued more and naturally OBP might be coming down as a result.
also, pitching is just insanely nasty now so that's another variable.