I'm very worried about the advent of "simulation" to try to gain a penalty or a card for the other team. We saw it in the Wales/Fiji game.
If it becomes prevalent then we're going the way of F**tball, (where the main object of the game is now to fall over in the penalty area) and I would be sad about having to stop watching rugby.
With all of the attention of head contacts, then it's an easy way for a cynical player to get the TMO to review, and the combination of :
(1) a freeze-frame showing a head contact, and
(2) a player on the floor appearing injured,
has a good chance of leading to a yellow/red card, no matter how inconsequential or glancing the contact is, or the (lack of) intent or foul play from the opponent. (I mean, a situation where a tackler has made all the right shapes, and the ball-carrier dips or is pushed down or folds on landing from a jump, without any time for tackler to react, and it leads to a small bump of heads or a glancing blow from which both players could continue.)
I hope that the referees & TMO have been briefed by World Rugby to stomp down hard on this, but it seems from the inconsistency of reffing in games so far that they're not very well prepared.