Looks like the Garmin Fenix 3 (and HR version) are finally getting the audio prompts. Requires this beta firmware https://www8.garmin.com/support/download_details.jsp?id=9504 announced a couple of days ago.
These will probably further make their way to yet more devices, notably the 920. Often there is a significant delay.
Also, (Tobais again, ty) the data encryption also included in v3.3 (above) has been upgraded to handle the issues discussed here, probably.