There is only one program left and one version of T&C´s. The "Benefits Overview" on both marriott.com and spg.com website refer to the same T&C´s:
Loyalty Program Terms & Conditions
Three "Legacy Programs" are unified to one "Loyalty Program"
Effective in August 2018, the Marriott Rewards® Program, The Ritz-Carlton Rewards Program, and the Starwood Preferred Guest® Program (the “SPG Program”) (each a “Legacy Program”), that were previously operated by Marriott International, Inc. and its subsidiaries, including Marriott Rewards, LLC and Preferred Guest, Inc. (collectively, the “Company”) as three separate programs, will function as one unified program (hereinafter, the “Loyalty Program”) while keeping their separate names for the time being for certain limited purposes.
The Loyalty Program will operate under one set of terms and conditions as set out below unless otherwise expressly stated (the “Program Rules”).
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4.2. b.:
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In 2018, the Loyalty Program will continue to honor Elite achievement via Qualifying Stays at participating SPG Brands that occur in 2018. Elite achievement via Qualifying Stays is only available until December 31, 2018 and will not be continued thereafter. Participating SPG Brands include: St. Regis® Hotels, The Luxury Collection®, W® Hotels, Sheraton®, Le Méridien®, Westin®, Tribute Portfolio®, Design Hotels TM, Four Points®, Aloft® Hotels and Element®. Members can earn Elite Status via Qualifying Stays under the requirements listed below:- Gold Elite: 10 to 24 Qualifying Stays or 25 to 49 Qualifying Nights
- Platinum Elite: 25 or more Qualifying Stays or 50 to 74 Qualifying Nights
4.2.c. Free Night Award stays will count toward Elite Night Credit.
So whether you book with your original Marriott Rewards account or your new second Rewards account (former SPG account) one stay at former Starwood properties should count as a stay towards elite for all stays until end 2018. I will merge my accounts (as soon as possible).