PA when an emergency descent is needed
I agree what is said at this critical moment is very important. It would also be a good idea to brief the PAX during the safety demo that besides the masks deploying if the cabin depressurizes, the aircraft needs to get to a lower altitude quickly and this will be a steep descent and may cause alarm but it quite normal.
I was on an airline within the past 18 months that did mention a descent if cabin pressure failed but didn't go any further. I can't remember which airline it was. So some are already doing a partial brief but all could go further and save a lot of angst if it happens.