FamilySearch is finally announcing it 2017 World Wide Indexing Event. It is scheduled to take place on October 20-22, 2017. The official website is here:
If you look closely, you can see that right now you could be one of the first 100 volunteers. I found out about the event through an email of the blog post above because I happen to be subscribed. But I am not sure how I would know about the event if I did not happen to subscribe to that particular blog. Perhaps if this event is worldwide, it needs some more publicity? There is a World Wide Indexing Event Facebook page but it is dated 2014.
I did find a few notices from others posting on Facebook, but nothing official.