New mulligan rule comes up next month!
Now, there's a some question.

Some players have a habit of looking at cards from top of library after he/she declared to take mulligan.
And, some players frequently start mulligan(shuffle his/her hand into library) before saying “Mulligan”.

The problem is here.
In the new rule, if the player who took more than 1 mulligan looked a card from the top of library without say anything, which should we deal it “He/she kept his/her hand and scry” or “He/she started mulligan”?
I think it should be mulligan, but it opens to question.

And, how can we catch up the cheating in those case?
(For example, looking the card before declare make it possible to decide whether mulligan or not with the information about the first draw).

I have a good feeling that there will be wholesale changes to the relevant policy (MTR/IPG) that will likely provide an answer. I recommend waiting for the Battle for Zendikar Release notes.

In addition to what Seth pointed out, we'll gain from the experiences during events using this new policy. Lessons learned from Pro Tour Origins and Worlds will likely be shared before anyone else has to deal with this issue.

I'll lock this thread for now, since it's too soon to really discuss further.

Thanks!