I think it happens by default. Believe it or not it will start to get too expensive for everyone to own all the cards they are playing with. There are groups out there right now such as teampossible and herons unlimited already having free decks for people to play. There is plenty of room for the rental market to pick up a lot of the slack once cards become more scarce, just a matter of adding players. Right now it's free mining for people that want to put the work in to acquire DEC, that will soon change in my humble opinion. Thanks for responding @apshamilton.