I found today that if you have the Marriott mobile app for iOS, you can tap your membership card and the reverse displays. Mine now states "Your Platinum Premier Elite Benefits..." rather than the front of the card, which displays my status as merely Platinum. (Also, not sure if the phone number to contact customer service is usually that for regular Plat Elites, or if the phone number gives it away also).
Those with the app on iOS 8 and who are plat elites, would you post your findings below? I'd like to see if this is an unpublished way of checking if you have earned/been renewed for Platinum Premier Elite status, before officially being notified by Marriott. Thanks!