Currently there is no event for map progress. The available events are LayerLoaded, SpatialReferenceChanged, and NavigationCompleted and the the awaitable Task LayersLoadedAsync. We are investigating functionality for the next major release which would actually allow you to determine when the mapview has completed rendering, rather than just when layers have finished downloading tiles, etc.
At a minimum there should be a way to detect that the map has started to draw and a way to detect when the map has totally finished drawing. I believe this is what you are describing. Given that capability we could display some notification to the user that the map is updating, maybe something simple like "Drawing..." in a status bar or an indeterminate progress bar. If you could provide the progress percentage (like the WPF API did) we could show a percentage progress bar that would give the user more feedback as to the progress of the map. I would vote for the percentage because it would give the developer more detail that can be passed onto the user.
Is this functionality still in the roadmap? If so, what version of the API can we expect this? I'm rendering a lot of features and have no indication whether or not it's still drawing?
Yes, it is on the roadmap for the next major release which we refer to as 'Quartz'. Some ArcGIS Runtime SDKs shipped their first Quartz Beta in the Fall last year - you can get an indication of the map progress design here: DrawStatusChangedListener| arcgis-android