The Vancouver Mulligan is here to stay! After a test run at Pro Tour: Magic Origins the new rule will be added to the comprehensive rules starting with the Battle for Zendikar Prerelease. Now when a player takes one (or more) mulligans, that player will also be able to scry 1 once a hand is kept.
In the official announcement, Director of R&D Aaron Forsythe cites the reception of "a lot of positive feedback regarding the change" as part of the decision making process to change the mulligan procedure.
The Vancouver Mulligan will officially take effect with the Battle for Zendikar Prerelease. It will be implemented on Magic Online during the Battle for Zendikar Prerelease events. It will also be used at the 2015 World Championships at the end of August.
The official rule:
103.4. Each player draws a number of cards equal to his or her starting hand size, which is normally seven. (Some effects can modify a player's starting hand size.) A player who is dissatisfied with his or her initial hand may take a mulligan. First, the starting player declares whether or not he or she will take a mulligan. Then each other player in turn order does the same. Once each player has made a declaration, all players who decided to take mulligans do so at the same time. To take a mulligan, a player shuffles his or her hand back into his or her library, then draws a new hand of one fewer cards than he or she had before. If a player kept his or her hand of cards, those cards become the player's opening hand, and that player may not take any further mulligans. This process is then repeated until no player takes a mulligan. (Note that if a player's hand size reaches zero cards, that player must keep that hand.) Then, beginning with the starting player and proceeding in turn order, any player whose opening hand has fewer cards than his or her starting hand size may scry 1