from what has been reported so far its only the upper levels of the game, who have experienced relentless, week in week out head knocks every day in training, that seem to be affected. Grass roots players who maybe train & play once a week don't seem to be generally impacted. Although I expect further work on this to be done.
I know this is not scientific but when I go into my rugby club, I see old rugby players propping up the bar with broken fingers, ruined noses & cauliflower ears, but they all seem to have their marbles still.