eGIS Associates have reminded us all that on December 4, 2018, Esri will be pushing a new update to ArcGIS Online. This update will include many changes. The biggest of which will be implementing new user types, going from 2 to 5 types.
Thanks eGIS for some clarification.
See also, this blog from Esri. In the post, Kelly Gerrow-Wilcox notes the following, “After the December 2018 update, additional user types—Editor, Field Worker, and GIS Professional—will be available for purchase”