Hi Craig,
Though integration with ArcGIS Enterprise (Portal) will be positive, I'm thinking of a scenario where an organization does not want to switch from AGOL to ArcGIS Enterprise (AGE??), but they still would like to host the Workforce data locally.
I may run into some terminology issues with the switch to ArcGIS Enterprise naming here so correct me if anything is wrong but basically an organization may host a on-premises ArcGIS Server (internal or publicly-accessible) instance but no Portal. They add services which are published on ArcGIS Server to their ArcGIS Online account as items, and all content for the organization is managed centrally in ArcGIS Online. They can have web maps stored as content items in ArcGIS Online that point to their local ArcGIS services. This is all good so far, and works fairly well (though being able to federate an on-premises ArcGIS Server with ArcGIS Online would complete the permissions picture nicely).
If this organization would now like to use Workforce but continue to manage their content items in ArcGIS Online, they need to currently have the assignments, dispatchers, workers and tracks as hosted feature layers. I'm wondering if there's an easy path forward that will allow an organization to re-publish these 4 feature services on a local ArcGIS Server instance, and then point the Workforce project and the web maps to these new on-premises services. Changing the web map of course is easily do-able, but there's no way of pointing the actual Workforce project itself to the new internal services. Of course, I've no idea whether the mobile app or the main dispatcher page would currently support this scenario.
Anyhow, that's another option for locally-hosted Workforce assignments and tracks that could potentially be considered, for those organizations who do want to stick with the hosted ArcGIS Online but still manage the data internally.