Here's the official info:
Scars of Mirrodin goes on sale in the Magic Online Store on Monday, October 18 at 9:00 AM PDT (16:00 UTC). Scars of Mirrodin becomes legal in ALL constructed formats following the October 13 downtime.
All appropriate Standard format Daily Events, Premier Events, Weekend Challenges, and Queues will switch to Scars of Mirrodin prize payouts after the scheduled downtime on Wednesday, October 20.
Scars of Mirrodin Release Events begin after the downtime Wednesday, October 20 and will consist of 5 parts:
- Scars of Mirrodin Booster Draft Queues
- Scars of Mirrodin 16-player Swiss Sealed Flights
- Scars of Mirrodin 64-Player "Top 8" Premier Drafts (beginning October 22)
- Scars of Mirrodin "Top 8" Swiss Sealed Events (beginning October 22)
- Scars of Mirrodin Release Events Championship (November 6)