Just called MR specialist on upcoming promotion, share some info as below.

1.Registration starts 8/19, should be available on MR account and notified by emails.
2.Promotion period from 9/15/15 to 1/15/16
Not sure if that's just me, account specific or general:
3.Earn double points starting 2nd paid stay, capped at 20,000 MR.

IMO not very impressive and I will wait for SPG fall promotion.