IIRC he announced this late 2017 during the bull run and was stated that he's still studying crypto and blockchain. And on latter of 2018, it's on the news that they have been hiring blockchain professionals which is an obvious act to understand that they will join and adopt the tech soon.

Creating a 'facebook coin' is likely but it's still a rumor, they have a large number of users so it will applicable to them. AFAIK, they have created sort of coins before during those restaurant city and farmville days.