And if someone attained Marriott Platinum by linking to a Platinum-level SPG account, then both accounts will have the same elite level and the same expiration.
In other words, if a Platinum SPG member linked his or her account to a base or Silver or Gold Marriott Rewards account this week, then that Rewards account would be Platinum too -- but only through the expiration date of the Platinum SPG level, not necessarily through all of 2017. If the SPG account qualifies for another year, then the Rewards elite level would continue too.