I have not received any "official" notification from Marriott. I reached 12 years with Marriott last year, have more than 1000 nights and 2.9 million points lifetime. So I should have Lifetime (Emeritus) Gold elite status and will get the last 100K points in the next few months for Lifetime Plat.
My lack of notification could be because I am currently a Plat and that "trumps" the Lifetime Gold status. It will be interesting to see if they send me anything in the next few months when I pass 3 million lifetime points.