I'd like to see the same option to enable popups on vector tiles that is available on tile layers. Currently if you're using a traditional cache tiled layer you can select a sublayer and enable popups by pointing it to an equivalent feature service. The same should be available on vector tiles.
Currently there is a large functionality gap in ArcGIS Online:
Dynamic data with low feature count = Feature Layer
Static data with high feature count = Tiled Layer
Dynamic data with high feature count = ?
This is the role previously used by dynamic map services, however those are only available via an internal ArcGIS Server. Hosted vector tiles work perfectly for this and perform incredibly well, but without the popup functionality they're basically alternative basemaps instead of useful operational layers.