I don't think you really have enough time left in the year to get any meaningful status with any other group, I would stick with Marriott this year for the Lifetime nights and then consider diversification in the new year. That is, unless you already have 20 or so nights with Hyatt or some other group already this year. Next year, achieve your 50 nights with Marriott and consider adding another. (Get a credit card for status with Hilton, I think even Platinum Amex gives you comp Gold status with Hilton, otherwise their own Amex cards will give you top status with them just for having it).