According to reddit, a booster pack of the upcoming Shadows over Innistrad expansion has leaked to the public. While unconfirmed, it appears that Transform (as indicated by the Checklist Card) and Madness are returning mechanics. New mechanics include:

The graveyard still matters on the second trip to Innistrad. Skulk may be the long sought "blue-black combat mechanic". We will find out more as we draw closer to Shadows over Innistrad's release on April 8th, 2016.