I'd assume it goes both ways: hitters can now study pitches more than ever before, whereas pitchers can study hitters' reactions and swings as well. Cool article.
It probably does, but if I had to guess, I'd still say the pitchers/defense have the advantage in this shift, partly because they are the initiators and the ones deliberately executing their move. The hitter, even if he knows the tendencies of pitchers, is still playing what is basically a reaction game (which is why the shifts are effective when you have the data on hitters).