On the Immersive Audio Facebook page, an audio preview of the Maddog X Cockpit Sound Immersion for Prepar3D was posted. Included in the audio preview are sounds of the cockpit ambiance, switches, and full GPWS test. Immersive Audio noted the sounds included in the preview will be exactly the same as the ones heard in the sim.
No release date has been set as the team is still looking for alternative ways to obtain proper recordings of crucial sounds for the sound pack. Immersive Audio is not sure when they will get new recordings due to the current situation, or if they will at all, due to airlines accelerating the retirement of their remaining MD80s. When more information is available, they will update the community. Below is the sound preview Immersive Audio uploaded to SoundCloud.